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Playing With Nodejs Console

Node.js is FUNMany of the readers might already aware/heard of Node.js but for ones who wanted to get a quick refresher of Node.js, following along. Node.js is associated with the following words: Open-Source and Cross-platform JavaScript runtime environment. Runs V8 JavaScript engine – core of google chrome. Is a single process but supports async I/O primitives. Helps in building applications which very performant and scalable. Handles thousands of concurrent connections with single server Helps in transiting front-end developers to back-end with ease. Supports ECMAScript standards. Support For Real-Time Applications. Unified Database Queries. Easy & Fast Coding i.e., Fast Development Cycle And many more. Shorter definition of Node.js is - it is an open-source, cross-platform JavaScript run-time environment (Google Chrome's V8 Engine) that executes JavaScript code outside of a browser. Let’s developers use JavaScript to write command line tools and for server-side scripting—running scripts server-side to produce dynamic web page content before the page is sent to the user's web browser. Usage of NodeJSNode.js is majorly used for the following scenarios: Backend and Servers  Microservices Development of API Front end Script and automation With all the advantages mentioned, Node.js is great in prototyping and agile developments, building superfast and highly scalable services. Are there any real time users who gained from Node.js? Yes, in fact there are hundreds of companies using and few to mention are Netflix heavily uses data streaming which is complex and requires uninterrupted streaming of data by different devices and sources. In wireless connectivity, one of the major challenges is bandwidth consumption. A reliable source that collects data and sends it to the rightful destination can be a challenge. GoDaddy use node.js for building their back-end infrastructure to increase its uptime and provide a non-blocking service handling multiple requests. Ebay is using node.js for pushing and to collect real-time data. Walmart is another company which uses node.js heavily. Infact, paypal has rebuild one of their applications in node.js which improved their efficiency with 33% fewer lines of code and 2X request/sec & 35% faster response time. May be now with the proven record of node.js usage, is everyone using it for the above advantages majorly or there are any other simple command line apps and utilities? Yes, there are many and let’s list down few of them which might be useful in day-to-day work. Pre-requisites:Create a folder by name ConsoleModuleExamples. Navigate to the folder in the terminal and create a node project as described below: Enter the command `npm init`. Expect few details to fill like PackageName etc, go with defaults wherever possible.  For other inputs, fill the required data. On prompt, if everything is Okay. Enter yes to confirm. Package.json file should be created with main pointing to index.js file. {    "name": "consolemoduleexamples",    "version": "1.0.0",    "description": "",    "main": "index.js",    "scripts": {      "test": "echo \"Error: no test specified\" && exit 1"    },    “type”: “module”,    "author": "",    "license": "ISC"  } Create an index.js file and add the below content. console.log('Hello world'); Run node index.js to see the ‘Hello world’ response in terminal. Note: For the below examples, make sure to install the specific module before running the example like npm install npm-name. Also, if there is a warning related to ES module, set "type": "module" in the package.json or use the .mjs extension. List of Command Line Apps more often used‘npm-name' is used for checking if there is any package available in npm or not.  Copy the below code and replace the content in index.js. Run node index.js in terminal. import npmName from 'npm-name';  // Check a package name  console.log(await npmName('npm-name')); // returns false  // Check an organization name  console.log(await npmName('@consolemoduleexamples')); // returns true 'Speed-test’ is used for testing internet connection and ping via speedtest.net website but from command line interface. ‘ESLint’ is for linting – a node.js command line app 'cpy’ is another simple command line app for copying files in a fast and user friendly manner. import cpy from 'cpy';  await cpy(['src/*.png', '!src/liger.png'], 'dist');  console.log('files copied successfully!'); Note: To verify this code, make sure to create two folders inside the project with name src and dist. With src containing files namely tiger.png, lion.png and liger.png. Post execution, tiger.png and lion.png files should be copied to dist as shown below. ‘empty-trash’ for cleaning up the Trash. import emptyTrash from 'empty-trash';  await emptyTrash();  console.log('Trash cleaned!'); ‘http-server’ that is powerful to serve static files. Also useful for learning, testing and local development. ‘jsinspect’ is another command line app for maintaing code quality without duplicate code. Also helps in extracting boilerplate or logical snippet of code. ‘browser-run’ helps in running automation test suites within the environment of our browser. ‘wifi-password’ - people like me who forget passwords can use this to figure out the password. Very handyimport wifiPassword from 'wifi-password';  const password = await wifiPassword();  console.log(password); Note: When executing this code, OS will request for access permissions. And many more... List of Command Line utilities more often usedget-stdin’ - this utility helps in simplifying work with stdin by getting it as a string or buffer.  import getStdin from 'get-stdin';  const str = await getStdin();  console.log(str); 'Chalk’ is a string styling utility for clean, focused and alternative to colors.js by eliminating some common problems with colors.js. ‘update-notifier’ is a utility tool tonotify the updates of the dependent packages in a non-intrusive way. ’configstore’ is used for loading and persisting configurations. ‘figures’ helps in getting unicode symbols with windows CMD fallbacks. ‘string-width’ helps in identifying the string width in different languages. Helps in validating. import stringWidth from 'string-width';   console.log(stringWidth('平仮名')); // 6   console.log(stringWidth('a')); // 1 'cli-table’ helps in displaying the data in table format with customizable characters, background styling, column width customization etc. ‘multispinner’ is one of the tools majorly used in displaying the progress of multiple actions with each one controlled separately but executed simultaneously.‘ansi-escapers’ is used for ANSI escape codes in the terminal and simplifies our daily work. And many more... With Node.js, we can build and use lot of command line apps and utilities which can make us productive and its lot fun to work with them.Console ModuleNode.js comes up with lot of global objects in global namespace which are available in all modules. Few to name are Console, global, process etc and we would be covering in detail about one such module called Console.  Node.js version comes up with two version one is Console class and another is global console instance which is pre-configured to process.stdout and process.stderr. Note: Console object is similar javascript console mechanism provided by web browsers. But they are not consistently synchronous like browser APs and at same time they are not asynchronous like node.js streams. They depend on the system I.e. Windows or POSIX. Reference - https://nodejs.org/api/process.html#a-note-on-process-io. Few of the methods available in console are captured below in browser console window: Below is an example of global console object which can be used in a node file (index.js in previous examples): console.log('hello world');  // Prints: hello world, to stdout as we are using the global console  console.log('hello %s', 'world');  // Prints: hello world, to stdout with an argument  const greeting = 'hello';  console.log(`${greeting} world`);  // Prints: hello world, to stdout with an external variable  console.warn(`Warning! Invalid format.`);  // Prints the warning message in warning color  console.info('Info - Logged info successfully.')  // Prints the info, similar to log.  console.error('Error occured while processing.');  // Print the error with the given error message. Console Instance instead of global ConsoleSimilar to global console object, we can create the instance of Console class and log the same information. (replace below content in index.js file) import { stdin, stdout } from 'process';  const myConsole = new console.Console(stdout, stdin);  myConsole.log('hello world');  // Prints: hello world, to stdout as we are using the global console  myConsole.log('hello %s', 'world');  // Prints: hello world, to stdout with an argument  const greeting = 'hello';  myConsole.log(`${greeting} world`);  // Prints: hello world, to stdout with a external variable The global console and the new console instance use the same output i.e., process.stdout and process.stderr. In case if you are wondering why we have two approaches then here is the reason. Console instance with different stream instance other than defaultThe parameters passed to the Console class we have one or two writable stream instances. First argument stdout is used by log or info methods and the second argument stderr is used for warning or error output. And more importantly we can configure the stream to be other stream instance like file system as shown below. Steps: Hope we are in sample folder consolemodules in terminal. Install fs module using npm i.e., npm install fs Copy the below snippet of code to index.js file. Run node index.js from terminal. Post execution, there should be two files created with names stdout.log and stderr.log containing log and warn message respectively. import fs from 'fs';  const output = fs.createWriteStream('./stdout.log');  const errorOutput = fs.createWriteStream('./stderr.log');  // Custom simple logger  const logger = new console.Console({ stdout: output, stderr: errorOutput });  // use it like console  logger.log('hello world');  // it is written to stdout.log file  logger.warn('Warning message');  // it is written to stderr.log file Note: Debug, Info are alias for log method whereas warn is an alias for error method. Internally they use the util.format() for formatting the message. Overview of API’s Method(s): time, timeLog and timeEnd. Console module is associated with timer to compute the duration of an operation. It exposes the below methods: time – takes a label to which the timer to be associated. timeEnd – takes a label which is used for time method as well to end the timer. timeLog – takes a label which is used for time method and prints the elapsed time and additional data. Example - Replace the content of index.js with below code and execute node index.js in terminal: console.time('process'); // starts the timer and associate with label process.  const value = 42; // imagine a expensive operation.  console.timeLog('process', value);  // prints the time elapsed.  console.timeEnd('process');  // prints the total time taken from call to time to timeEnd. Method(s): group, groupCollapsed and groupEnd. Another set of methods related to indentation are group, groupCollapsed(alias of group) and groupEnd. Below is a snap in browser console. Method(s): count Console maintains an internal counter based on label to count with count method. And for resetting the counter there is another method countReset. Below is a snap in browser console. Method(s): dir To log information to a stdout, we can use log method but to capture the entire object and display an interactive list of properties we can rely on ‘console.dir’. Below is a snap in browser console. Method(s): table Another useful method to display the array of objects in tabular form is ‘console.table’ with an optional argument of properties to be displayed in tabular form. Below is a snap in browser console. Building a Custom logger with file stream H2 Install fs and util modules using npm if they aren’t installed. (Continuation of previous examples) Replace the content of index.js file with the below example code. Execute node index.js to see the logger working. Post-execution, stdout.log should contain all the logs as shown below in output section with color coding. Custom logger built using file stream: import util from 'util';  import fs from 'fs';    const output = fs.createWriteStream('./stdout.log');   const errorOutput = fs.createWriteStream('./stderr.log');     // Simple logger   const logger = new console.Console({stdout: output,   stderr: errorOutput,   inspectOptions: {   // Maximum number of Array elements to include when formatting.   maxArrayLength: 3,   // Maximum number of characters to include when formatting.   maxStringLength: 10,   // If properties of an object are sorted   sorted: true,   // Remember to enable the color mode. Default is false.   colors: true   }}   );   // display first 10 characters   logger.log('log: object', {attr: 'string content a b c d e f g h i j k'});   // log: object { attr: ‘string content a b c’… 16 more characters }     // display first 3 items   logger.log('log: array', ['array_value1', 'array_value2', 'array_value3', 'array_value4', 'array_value5']);   // log: array [ ‘array_value1’, ‘array_value2’, ‘array_value3’, … 2 more items ]   // sorted array is displayed   logger.log('log: set', new Set([3, 1, 2, 5, 4]));   // log: set Set(5) { 1, 2, 3, 4, 5 }     // number styling is changed to blue   util.inspect.styles.number = 'blue';   // numbers are shown in blue     logger.log('log: set', new Set([30, 10, 20, 50, 40]));   // log: set Set { 10, 20, 30, 40, 50 } Output:All the things one can do with NodeJS The Console class can be used to create a logger with configurable output streams and for the basic usage we can rely on the global console which has predefined configuration of Process.stdin and process.stderr.  Based on the configurable output stream and the platform, they can be synchronous or asynchronous which helps the processing/logging to be offloaded. 

Playing With Nodejs Console

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Playing With Nodejs Console

Node.js is FUN

Many of the readers might already aware/heard of Node.js but for ones who wanted to get a quick refresher of Node.js, following along. 

Node.js is associated with the following words: 

  • Open-Source and Cross-platform JavaScript runtime environment. 
  • Runs V8 JavaScript engine – core of google chrome. 
  • Is a single process but supports async I/O primitives. 
  • Helps in building applications which very performant and scalable. 
  • Handles thousands of concurrent connections with single server 
  • Helps in transiting front-end developers to back-end with ease. 
  • Supports ECMAScript standards. 
  • Support For Real-Time Applications. 
  • Unified Database Queries. 
  • Easy & Fast Coding i.e., Fast Development Cycle 
  • And many more. 

Shorter definition of Node.js is - it is an open-sourcecross-platform JavaScript run-time environment (Google Chrome's V8 Engine) that executes JavaScript code outside of a browser. Let’s developers use JavaScript to write command line tools and for server-side scripting—running scripts server-side to produce dynamic web page content before the page is sent to the user's web browser. 

Usage of NodeJS

Node.js is majorly used for the following scenarios: 

  • Backend and Servers  
  • Microservices 
  • Development of API 
  • Front end 
  • Script and automation 

With all the advantages mentioned, Node.js is great in prototyping and agile developments, building superfast and highly scalable services. Are there any real time users who gained from Node.js? Yes, in fact there are hundreds of companies using and few to mention are 

  • Netflix heavily uses data streaming which is complex and requires uninterrupted streaming of data by different devices and sources. 
  • In wireless connectivity, one of the major challenges is bandwidth consumption. A reliable source that collects data and sends it to the rightful destination can be a challenge. GoDaddy use node.js for building their back-end infrastructure to increase its uptime and provide a non-blocking service handling multiple requests. 
  • Ebay is using node.js for pushing and to collect real-time data. 
  • Walmart is another company which uses node.js heavily. 
  • Infact, paypal has rebuild one of their applications in node.js which improved their efficiency with 33% fewer lines of code and 2X request/sec & 35% faster response time. 

May be now with the proven record of node.js usage, is everyone using it for the above advantages majorly or there are any other simple command line apps and utilities? Yes, there are many and let’s list down few of them which might be useful in day-to-day work. 

Pre-requisites:

  • Create a folder by name ConsoleModuleExamples. 
  • Navigate to the folder in the terminal and create a node project as described below: 
  • Enter the command `npm init`. 
  • Expect few details to fill like PackageName etc, go with defaults wherever possible.  
  • For other inputs, fill the required data. 
  • On prompt, if everything is Okay. Enter yes to confirm. 
  • Package.json file should be created with main pointing to index.js file. 
{ 
  "name": "consolemoduleexamples", 
  "version": "1.0.0", 
  "description": "", 
  "main": "index.js", 
  "scripts": { 
    "test": "echo \"Error: no test specified\" && exit 1" 
  }, 
  “type”: “module”, 
  "author": "", 
  "license": "ISC" 
} 
  • Create an index.js file and add the below content. 

console.log('Hello world'); 

  • Run node index.js to see the ‘Hello world’ response in terminal. 

Note: For the below examples, make sure to install the specific module before running the example like npm install npm-name. Also, if there is a warning related to ES module, set "type": "module" in the package.json or use the .mjs extension. 

List of Command Line Apps more often used

  • npm-name' is used for checking if there is any package available in npm or not.  
    • Copy the below code and replace the content in index.js. 
    • Run node index.js in terminal. 
import npmName from 'npm-name'; 
// Check a package name 
console.log(await npmName('npm-name')); // returns false 
// Check an organization name 
console.log(await npmName('@consolemoduleexamples')); // returns true 
  • 'Speed-test’ is used for testing internet connection and ping via speedtest.net website but from command line interface. 
  • ‘ESLint’ is for linting – a node.js command line app 
  • 'cpy’ is another simple command line app for copying files in a fast and user friendly manner. 
import cpy from 'cpy'; 
await cpy(['src/*.png''!src/liger.png'], 'dist'); 
console.log('files copied successfully!'); 

Note: To verify this code, make sure to create two folders inside the project with name src and dist. With src containing files namely tiger.png, lion.png and liger.png. Post execution, tiger.png and lion.png files should be copied to dist as shown below. 

Playing With Nodejs Console

  • empty-trash’ for cleaning up the Trash. 

import emptyTrash from 'empty-trash'; 
await emptyTrash(); 
console.log('Trash cleaned!'); 
  • ‘http-server’ that is powerful to serve static files. Also useful for learning, testing and local development. 
  • ‘jsinspect’ is another command line app for maintaing code quality without duplicate code. Also helps in extracting boilerplate or logical snippet of code. 
  • ‘browser-run’ helps in running automation test suites within the environment of our browser. 
  • ‘wifi-password’ - people like me who forget passwords can use this to figure out the password. Very handy
import wifiPassword from 'wifi-password'; 
const password = await wifiPassword(); 
console.log(password); 

Note: When executing this code, OS will request for access permissions. 

  • And many more... 

List of Command Line utilities more often used

  • get-stdin’ - this utility helps in simplifying work with stdin by getting it as a string or buffer. 

 import getStdin from 'get-stdin'; 
const str = await getStdin(); 
console.log(str); 
  • 'Chalk’ is a string styling utility for clean, focused and alternative to colors.js by eliminating some common problems with colors.js. 
  • ‘update-notifier’ is a utility tool tonotify the updates of the dependent packages in a non-intrusive way. 
  • ’configstore’ is used for loading and persisting configurations. 
  • ‘figures’ helps in getting unicode symbols with windows CMD fallbacks. 
  • ‘string-width’ helps in identifying the string width in different languages. Helps in validating. 
import stringWidth from 'string-width';  
console.log(stringWidth('平仮名')); // 6  
console.log(stringWidth('a')); // 1 
  • 'cli-table’ helps in displaying the data in table format with customizable characters, background styling, column width customization etc. 
  • ‘multispinner’ is one of the tools majorly used in displaying the progress of multiple actions with each one controlled separately but executed simultaneously.

Playing With Nodejs Console

  • ‘ansi-escapers’ is used for ANSI escape codes in the terminal and simplifies our daily work. 
  • And many more... 

With Node.js, we can build and use lot of command line apps and utilities which can make us productive and its lot fun to work with them.

Console Module

Node.js comes up with lot of global objects in global namespace which are available in all modules. Few to name are Console, global, process etc and we would be covering in detail about one such module called Console.  

Node.js version comes up with two version one is Console class and another is global console instance which is pre-configured to process.stdout and process.stderr. 

NoteConsole object is similar javascript console mechanism provided by web browsers. But they are not consistently synchronous like browser APs and at same time they are not asynchronous like node.js streams. They depend on the system I.e. Windows or POSIX. Reference - https://nodejs.org/api/process.html#a-note-on-process-io. 

Few of the methods available in console are captured below in browser console window: Playing With Nodejs Console

Below is an example of global console object which can be used in a node file (index.js in previous examples): 

console.log('hello world'); 
// Prints: hello world, to stdout as we are using the global console 
console.log('hello %s''world'); 
// Prints: hello world, to stdout with an argument 
const greeting = 'hello'; 
console.log(`${greeting} world`); 
// Prints: hello world, to stdout with an external variable 
console.warn(`Warning! Invalid format.`); 
// Prints the warning message in warning color 
console.info('Info - Logged info successfully.') 
// Prints the info, similar to log. 
console.error('Error occured while processing.'); 
// Print the error with the given error message. 

Console Instance instead of global Console

Similar to global console object, we can create the instance of Console class and log the same information. (replace below content in index.js file) 

import { stdinstdout } from 'process'; 
const myConsole = new console.Console(stdoutstdin); 
myConsole.log('hello world'); 
// Prints: hello world, to stdout as we are using the global console 
myConsole.log('hello %s''world'); 
// Prints: hello world, to stdout with an argument 
const greeting = 'hello'; 
myConsole.log(`${greeting} world`); 
// Prints: hello world, to stdout with a external variable 

The global console and the new console instance use the same output i.e., process.stdout and process.stderr. In case if you are wondering why we have two approaches then here is the reason. 

Console instance with different stream instance other than default

The parameters passed to the Console class we have one or two writable stream instances. First argument stdout is used by log or info methods and the second argument stderr is used for warning or error output. And more importantly we can configure the stream to be other stream instance like file system as shown below. 

Steps: 

  • Hope we are in sample folder consolemodules in terminal. 
  • Install fs module using npm i.e., npm install fs 
  • Copy the below snippet of code to index.js file. 
  • Run node index.js from terminal. 
  • Post execution, there should be two files created with names stdout.log and stderr.log containing log and warn message respectively. 
import fs from 'fs'; 
const output = fs.createWriteStream('./stdout.log'); 
const errorOutput = fs.createWriteStream('./stderr.log'); 
// Custom simple logger 
const logger = new console.Console({ stdout: outputstderr: errorOutput }); 
// use it like console 
logger.log('hello world'); 
// it is written to stdout.log file 
logger.warn('Warning message'); 
// it is written to stderr.log file 

Note: Debug, Info are alias for log method whereas warn is an alias for error method. Internally they use the util.format() for formatting the message. 

Overview of API’s 

Method(s): time, timeLog and timeEnd. 

Console module is associated with timer to compute the duration of an operation. It exposes the below methods: 

  • time – takes a label to which the timer to be associated. 
  • timeEnd – takes a label which is used for time method as well to end the timer. 
  • timeLog – takes a label which is used for time method and prints the elapsed time and additional data. 

Example - Replace the content of index.js with below code and execute node index.js in terminal: 

console.time('process'); // starts the timer and associate with label process. 
const value = 42// imagine a expensive operation. 
console.timeLog('process'value); 
// prints the time elapsed. 
console.timeEnd('process'); 
// prints the total time taken from call to time to timeEnd. 

Method(s): group, groupCollapsed and groupEnd. 

Another set of methods related to indentation are group, groupCollapsed(alias of group) and groupEnd. 

Below is a snap in browser console. Playing With Nodejs Console

Method(s): count 

Console maintains an internal counter based on label to count with count method. And for resetting the counter there is another method countReset. 

Below is a snap in browser console. Playing With Nodejs Console

Method(s): dir 

To log information to a stdout, we can use log method but to capture the entire object and display an interactive list of properties we can rely on ‘console.dir’. 

Below is a snap in browser console. Playing With Nodejs Console

Method(s): table 

Another useful method to display the array of objects in tabular form is ‘console.table’ with an optional argument of properties to be displayed in tabular form. 

Below is a snap in browser console. Playing With Nodejs Console

Building a Custom logger with file stream H2 

  • Install fs and util modules using npm if they aren’t installed. (Continuation of previous examples) 
  • Replace the content of index.js file with the below example code. 
  • Execute node index.js to see the logger working. 
  • Post-execution, stdout.log should contain all the logs as shown below in output section with color coding. 

Custom logger built using file stream: 

import util from 'util'; 
import fs from 'fs'; 
 
const output = fs.createWriteStream('./stdout.log');  
const errorOutput = fs.createWriteStream('./stderr.log');  
 
// Simple logger  
const logger = new console.Console({stdout: output,  
stderr: errorOutput,  
inspectOptions: {  
// Maximum number of Array elements to include when formatting.  
maxArrayLength: 3,  
// Maximum number of characters to include when formatting.  
maxStringLength: 10,  
// If properties of an object are sorted  
sorted: true,  
// Remember to enable the color mode. Default is false.  
colors: true  
}}  
);  
// display first 10 characters  
logger.log('log: object', {attr: 'string content a b c d e f g h i j k'});  
// log: object { attr: ‘string content a b c’… 16 more characters }  
 
// display first 3 items  
logger.log('log: array', ['array_value1''array_value2''array_value3''array_value4''array_value5']);  
// log: array [ ‘array_value1’, ‘array_value2’, ‘array_value3’, … 2 more items ]  
// sorted array is displayed  
logger.log('log: set'new Set([31254]));  
// log: set Set(5) { 1, 2, 3, 4, 5 }  
 
// number styling is changed to blue  
util.inspect.styles.number = 'blue';  
// numbers are shown in blue  
 
logger.log('log: set'new Set([3010205040]));  
// log: set Set { 10, 20, 30, 40, 50 } 

Output:Playing With Nodejs Console

All the things one can do with NodeJS 

The Console class can be used to create a logger with configurable output streams and for the basic usage we can rely on the global console which has predefined configuration of Process.stdin and process.stderr.  

Based on the configurable output stream and the platform, they can be synchronous or asynchronous which helps the processing/logging to be offloaded. 

Sumanth

Sumanth Reddy

Author

Full stack,UI Architect having 14+ Years of experience in web, desktop and mobile application development with strong Javascript/.Net programming skills .Strong experience in microsoft tech stack and Certified in OCI associate. Go-to-guy on integration of applications, building a mobile app by zeroing on tech stack. Majorily experienced on engineering based IIOT products and Marekting Automation products deployed on premise and on-cloud. 

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Angular: Add service to module Code Example

What are services in an Angular app?Services is a general term broadly categorized as values, functions, or features that our application may need. Services are made to reuse codes designed for a purpose.Angular services differentiate an element from its service so that the services can be re-used. This increases the modularity of the Angular application. Service in an Angular App can be almost anything, it can be an element, a component, or it can be a module used for some specific purpose.All services in Angular App are classes with a definite purpose. It serves a purpose and serves it well.Some of the very well-known services include:Logging Service: Used for logging in, logging out.Data Fetching: Fetching Data and representing it in a formatted way.Data Service: Fetching and receiving Data.Message Bus: Used for communicating through a set of shared interfaces.Tax Calculator: Calculating Tax by synchronizing with the current Law system.EMI calculator: Easy Monthly Instalment Calculator, mainly used in calculations related to Loan. Application Configuration: Common configuration throughout the application support.ReusabilityReusability is very important when building large-scale applications. Classes built for a common purpose should not be required to be built again and again. This even causes misinterpretation of certain important classes. We need to implement separation of concerns to segregate different classes used for different purposes. This can be achieved by Angular services.In Angular 13 Framework, the services are those objects that get instantiated a maximum of one time during the entire lifetime of any Angular application or Angular module.All the Angular Services contain many methods that maintain data throughout the lifetime of an application. Thus, it has become a medium to share various responsibilities within one or multiple components.Services and Dependency InjectionServices provide us with injectable features. The Angular App provides us the decorator @Injectable for creating a service. Classes thereby created can be injected into any other module or component by calling it through service provider modules.The two-step process for creating a service in Angular application is:Use @Injectable decorator to create a class.Use Dependency Injection to inject the class or register the class with the service provider.In Angular 13 Framework, one of the ways of performing DI – Dependency Injection is by using Service injection. Dependencies are services or objects of a class that helps in performing its function. Dependency injection or DI are design patterns in which a class demands dependencies from external sources rather than constructing them.Building and providing servicesLet us build a service for keeping Records of Employees:Step 1: Install Node.js:Angular requires Node.js version 14.X.X or later. You can download it fromhttps://nodejs.org/en/download/The latest Version is : node-v16.13.1-x64Install node.js once downloaded:Once you have installed Node.js on your system, open node.js command prompt.To check your version, run node -v in a terminal/console window.Step 2: Use npm to Install Angular CLIUse the following command to install Angular CLInpm install -g @angular/cli Ornpm install -g @angular/cli@latestOrJust go to Angular CLI official website https://cli.angular.io/You will see the whole cli command to create an Angular app. You need to run the first command to install Angular CLI. These steps are same for Windows and Mac.To check Node and Angular CLI version, use ng --version command.Step 3: Create an app called ngApp4ServiceSyntax:ng new app_nameC:\>ng new ngApp4Service It asks forWould you like to add Angular routing? YesWhich stylesheet format would you like to use?> CSS….Step 4: Generate Service via CLI:Syntax for creating a service:ng generate service [options]ng g service [options]Let us generate the required service: here we are going to create “Employee” Service.Go to the app folder and install the required service: “Employee”:Step 5: Edit the service ts file:Service to store Employee Data: employee.service.tsFile name: employee.service.tsimport { Injectable } from '@angular/core'; @Injectable({ providedIn: 'root' }) export class EmployeeService { public _empList: Array = [];       constructor() {           this._empList = [{name:'Jay Choudhury', city:'Ghaziabad'}];       }        returnEmpData(): Array {           return this._empList;       }        addEmpData(item: any): void {           this._empList.push(item);       }   }Step 6: Import the employee service:Import the service in the app.module.ts:import { BrowserModule } from '@angular/platform-browser';   import { NgModule, NO_ERRORS_SCHEMA } from '@angular/core';   import { FormsModule, ReactiveFormsModule } from '@angular/forms';   import { AppComponent } from './app.component';   import { EmployeeService } from './employee.service';   @NgModule({     declarations: [       AppComponent     ],     imports: [       BrowserModule, FormsModule, ReactiveFormsModule     ],     providers: [EmployeeService],     bootstrap: [AppComponent],     schemas: [NO_ERRORS_SCHEMA]   })   export class AppModule { }Step 7: Use the service: Employee:Edit: app.component.tsimport { Component, OnInit } from '@angular/core';   import { EmployeeService } from './employee.service';   @Component({       selector: 'app-root',         templateUrl: './app.component.html',         styleUrls : ['./app.component.css']         })   export class AppComponent implements OnInit {         public model: any = {};         public source: Array;         constructor(public service: EmployeeService) {               this.source = this.service.returnEmpData();               }          ngOnInit(): void { }          public submit(): void {               if (this.validate()) {                   this.service.addEmpData(this.model);                   this.reset();               }           }         public reset(): void {          this.model = {};      }          public validate(): boolean {                  let status: boolean = true;                  if (typeof (this.model.name) === "undefined") {                         alert('Name is Blank');                         status = false;                         return status;                        }                  else if (typeof (this.model.city) === "undefined") {                         alert('City is Blank');                         status = false;                         return status;                        }                  return status;           }    }Edit app.component.html:         Employee Form             Employee Name                       City                                           Employee Details                                         Employee's Name                     City                                   {{item.name}}                         {{item.city}}                                     Step 8: Run to check the service:Go to the app folder:C:\>ng serveRun at localhost:http://localhost:4200/We get the Employee Form.We can add more details for the employee, and see the result.Importance of ServicesAngular App provides Angular Services as re-usable components of the application. It uses @Injectable Decorator for building a Service. A service can be called through multiple components as a common element and shared for various purposes. This helps in avoiding repetitive work and improves the speed of app development.
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Angular: Add service to module Code Example

What are services in an Angular app?Services is ... Read More

Create GraphQL API with example

Recently, GraphQL has made a lot of buzz among the developer community, and it has been receiving a lot of attention because of its dynamic nature along with its capability to fetch data, which is a lot less redundant. In this Code Tutorial, you will get to learn about what GraphQL really is, why has it created such hype amongst new-age developers, how is it different from the REST approach, and finally you will be building our own API with GraphQL along with Code Tutorials. Let’s get started!What is GraphQL? A quick primerBefore understanding what GraphQL is, let’s first understand what Query Languages are. Query Languages are computer languages that request the data from a database (called queries) to a client-side application through a server. A well-known example is Structured Query Language or SQL.Coming to GraphQL, by definition - “GraphQL is an open-source data query and manipulation language for APIs, and a runtime for fulfilling queries with existing data” (source: Wikipedia). Simply put, GraphQL is a new age Query Language developed by Facebook in 2012 that helps Application Programming Interfaces (APIs) fetch only that data which is requested by the client, and nothing else. This enormously reduces the redundant data at the API endpoint and making the requests blazing fast and developer friendly.Initially, GraphQL was an internal project of Facebook and it was created for fetching specific data and reducing network usage. In 2015, it was released publicly at the React.js conference and reference implementations and specifications of GraphQL in JavaScript were open-sourced. Later most of the programming languages adopted that. New languages like Python, Node.js, Java, C#, PHP, GO, and many more, support GraphQL.But wasn’t the same thing already being done by RESTful APIs? The answer is yes, but GraphQL is different than REST in a lot of ways.GraphQL is Client-Driven, whereas REST is Server-Driven.Queries are organized in terms of Schema and strict typecasting in GraphQL, whereas REST has Endpoints for that task.GraphQL calls Specific data with a single call. REST calls Fixed data with multiple calls.Instead of the GET, POST, PUT, DELETE operations in REST, GraphQL has Query, Mutation, and Subscription for data manipulation.Some of the other advantages of using GraphQL are:GraphQL is faster than other communication APIs.GraphQL can retreat multiple resources and results with a single request.It is easy to use complex systems and microservices with GraphQL as it unifies and hides their complexity.It offers multiple libraries and powerful tools for various projects such as GraphiQL, GraphQL Explorer, Apollo.No under and over data fetching. It fetches the amount of data that is required.The core building block of GraphQL is its schema which is used as a middle way between server and client while defining the accessibility of the data.  A GraphQL schema is written in Schema Definition Language (SDL) and refers to the exact mutations and queries that a client can execute against your data graph. It can be built with any programming language. Simply, the schema defines the type of data that can be fetched, the relationships between these types of data, and what type of queries are allowed. The most basic components of a GraphQL schema are object types. They represent a kind of object you can fetch from your service along with the fields it has. Further, schema helps the client validate their query and eliminate unavailable data or the wrong structure stage.The other two fundamental parts of GraphQL are Query and Resolver. The request to fetch a particular data is called a query and a resolver is used to tell the server from where and how to fetch the data corresponding to the given field. You can execute the GraphQL queries either by Command line or by using a GraphQL server.GraphQL works in three parts – a query to read data, a mutation to write data, and a subscription to receive real-time data over time.Now that you know the ‘What’ and ‘Where’of GraphQL, let’s dive straight into our favorite part, the development phase.Let’s Play with GraphQLTo get started with GraphQL, you need a server that serves your API and a client that connects to your service endpoints. In this section, you will learn about a step-by-step procedure of building an API using GraphQL and Express on top of Node.js. In the next section, you will be implementing these prerequisites into code and start our development for the API.Prerequisites:Understanding of GraphQLNode Package Manager (or NPM) with version 10+Knowledge of basic querying and server-side programming.We will be needing a database to store the user data and everything else that a client-side application can request for. For this, you will be using LowDB, which is a simple file based JSON database for small projects in the localhost. Then you will be needing middleware to connect our database system to the requesting frontend application. For this, you will be using the Express middleware with the GraphQL implementation of Express - the Graphql-express library. Finally, you will be making a client-side application using react which can request all the data from the local database and can perform operations on the database like read, write, and delete.So, our roadmap is simple and straightforward. Create a Database Schema > Use a middleware server to query the database > Create a frontend application to use the data. If this is too much at once for you, do not worry as this is article is being written keeping in mind that the reader is a first-timer for GraphQL and basic querying as usual. Now, let’s dive into the code.Setting up Express GraphQLLet’s begin with the basic project structure of a Node.js application. Begin a new project in a new folder.$ mkdir graphql-example $ cd graphql-exampleUse NPM to intiialize a project$ npm init -yInstall the required dependencies for Express, MongoDB (Mongoose), and some additional dependencies required for the function of Express.$ npm install express mongoose body-parser cors --saveApollo Server is a community-maintained open-source GraphQL server that works with all Node.js HTTP server frameworks, so next, you are going to download and save that.$ npm install apollo-server-express --saveThis should’ve created a package.json and a package-lock.json file within your folder. These files contain information regarding our environment, the dependencies, and the specific versions to run those dependencies.This means our environment is ready and you can now start developing the integrated server and API. We are going to write the Schema inside the index.js file. In the index.js file, start off by writing this code.const express = require('express'); const mongoose = require('mongoose'); const schema = require('./schema'); const bodyParser = require('body-parser'); const cors = require('cors'); const { ApolloServer } = require('apollo-server-express'); const url = "mongodb://localhost:27017/moviesdb"; const connect = mongoose.connect(url, { useNewUrlParser: true }); connect.then((db) => {       console.log('Connected correctly to server!'); }, (err) => {       console.log(err); }); const server = new ApolloServer({       typeDefs: schema.typeDefs,       resolvers: schema.resolvers }); const app = express(); app.use(bodyParser.json()); app.use('*', cors()); server.applyMiddleware({ app }); app.listen({ port: 4000 }, () =>   console.log(`Server ready at  http://localhost:4000${server.graphqlPath}`));In lines number 1 to 6, you’re implementing the necessary modules. Note that here you have imported the ./schema, but you haven’t created that yet. We will be doing this in the next step.In lines number 9 to 14, you are connecting the project to the MongoDB database and logging any error you face to the console.In lines number 16 to 19, you’re creating a new Apollo Server with typeDefs and Resolver. We’ll be defining those in the ./schema later in this tutorial.In lines 21 to 26, you’re firing up the Express Server at port 4000, when you will actually be able to interact with what you’re building.GraphQL has two main principles to work: types and resolvers. We defined them in Apollo Server. We’ll import them from the file you’ll create later.Next, let’s create the file models/movie.js that’ll contain the movie-Mongoose model.const mongoose = require('mongoose'); const Schema = mongoose.Schema; const movieSchema = new Schema({     name: {        type: String,        required: true     },     rating: {        type: Number,        required: true     },     producer: {        type: String,        required: true    } }, {     timestamps: true }); var Movies = mongoose.model('Movie', movieSchema); module.exports = {Movies, movieSchema};We’re going to build a simple movie app, where you can show, add, edit, and delete movies. That way you’ll get through the basics of GraphQL, which is the main goal of this tutorial.In lines 4 to 19, you’re basically determining the schema of the database that is going to hold the data of movies. Every movie is going to have a Name and a Producer of type String and a Rating of type Number.Designing the SchemaLet’s move on to the schema.js file where you’re going to build our GraphQL API.Create a new file in the root of the folder by the name of schema.js and add the following code.const { gql } = require('apollo-server-express');   const Movie = require('./models/movie').Movies;   const typeDefs = gql `    type Movie {      id: ID!      name: String!      producer: String!      rating: Float!  }  type Query {    getMovies: [Movie]    getMovie(id: ID!): Movie  }  type Mutation {      addMovie(name: String!, producer: String!, rating: Float!): Movie      updateMovie(id: ID!, name: String!, producer: String!, rating: Float): Movie      deleteMovie(id: ID!): Movie    } `In this, you’re building the schema. We defined the Movie type which will have an ID, the name of the movie and the producer, and a rating of type Float. The “!” after the types shows that these fields are necessary.Unlike the REST approach of getting different tasks done at different endpoint URLs, GraphQL can create operations in a single endpoint. That is what you have done in line 11 onwards. The type Query determines the GET operations, and type Mutation determines the modification operations like POST, DELETE, etc. In getMovies, you’re returning a list of all available movies in our database, and in getMovie, you’re getting the specific movie by the ID of that movie.Now you’re going to link these with the Mongoose Database queries that are going to perform the actions in the database. And this is done by Resolvers. Resolvers are a collection of functions that connect schema fields and types to various backends. It can read, write, and delete data from and to anywhere in the database, be it SQL, NoSQL, or Graph-based database. In simple terms, they act as a GraphQL query handler. Here’s how you’re going to implement Resolvers in our code:const resolvers = {   Query: {     getMovies: (parent, args) => {       return Movie.find({});     },     getMovie: (parent, args) => {       return Movie.findById(args.id);     }   },   Mutation: {     addMovie: (parent, args) => {       let movie = new Movie({         name: args.name,         producer: args.producer,         rating: args.rating,       });       return movie.save();     },     updateMovie: (parent, args) => {       if (!args.id) return;         return Movie.findOneAndUpdate(          {            _id: args.id          },          {            $set: {              name: args.name,              producer: args.producer,              rating: args.rating,            }          }, {new: true}, (err, Movie) => {            if (err) {              console.log('Something went wrong when updating the movie');            } else {              continue;            }          }       );     }   } } module.exports = {typeDefs,resolvers};This is the basic logic of MongoDB and CRUD applications, which doesn’t come under the scope of this article, since it is majorly focused on GraphQL. However, the logic is simple and straightforward for anyone to understand, so skim through it once.With this, you’re done with a basic Movie API that can perform all the CRUD operations on a database of movies. To test this out, you’re going to fire up our node server and open the browser in http://localhost:4000/graphql which will open the GraphQL Playground.$ node index.js Server ready at http://localhost:4000/graphqlOnce the Playground UI opens, you’re first going to create a Movie Record for the database since it would initially be empty.mutation { addMovie(name: “GraphQL Movie”, producer: “Facebook”, rating:  4.5) { id, name, rating, producer } }OUTPUT:{ “data” : { “addMovie”: { “id”: “5j2j1lnk1LNS231MLK3”, “name”: “GraphQL Movie”, “producer”: “Facebook”, “rating”: 4.5 } } }And now let’s list out all the movies in the database with only their “name” and “rating”.query { getMovies: { name, rating } }OUTPUT:{ “Data”: { “getMovies”: [ { “name”: “GraphQL Movie”, “rating”: 4.5 } ] } }So, you have successfully created a Movie API where you can perform all the CRUD operations on a single endpoint, and also ask for just the data that you want.  This results in a blazing fast API response and a developer-friendly return object that makes development fast and easy.Using GraphQL with ReactUsing GraphQL with react is super easy and can make full-stack development look like a piece of cake. We’re going to build a react app that uses the Movie API you just built to render the results on a frontend client app.Start off by installing the required dependencies.$ npm install create-react-app graphql @apollo/clientCreate a new React appnpx create-react-app movies-appLet’s start off by initializing an ApolloClient instance. In index.js let's first import the symbols you need from @apollo/client, Next, you'll initialize ApolloClient, passing its constructor a configuration object with URI and cache fields:import {   ApolloClient,   InMemoryCache,   ApolloProvider,   useQuery,   gql } from "@apollo/client"; const client = new ApolloClient({   uri: 'https://48p1r2roz4.sse.codesandbox.io',   cache: new InMemoryCache() });The URI specifies the GraphQL Server URL.That’s it! Our client app is ready to fetch data from the GraphQL server. In index.js, let’s wrap our React app with the ApolloProvider Component. Put up the ApolloProvider somewhere high in the app, above any component that might need to access GraphQL data.function App() {   return (           My first GraphQL app       ); } render(         ,   document.getElementById('root'), );With this being done, our client app is now ready to request data from the server and perform queries on the frontend. We can do this using the useQuery React Hook that shares the GraphQL data with the UI.In the index.js, let’s first define the query you want to execute.const MOVIES = gql`   query getMovies {      name,      producer   } `;Next, let's define a component called GetMovies that executes our getMovies query with the useQuery hook:function GetMovies() {   const { loading, error, data } = useQuery(MOVIES);   if (loading) return Loading...;   if (error) return Error :(;   return data.map(({ name, producer }) => (                   {name}: Produced by {producer}             )); }Whenever this component renders, the useQuery hook automatically executes our query and binds the results to the data property on successful completion of the query.Finally, you'll add GetMovies to our existing component tree:function App() {   return (           My first Apollo app             ); }When your app reloads, you should briefly see a loading indicator, followed by a list of Movies present in the MongoDB database.Congratulations. You just made a React app that uses GraphQL to render data from the server. Give yourself a pat on the back for this one.Dev-friendly Query Languages are the FutureSo, wrapping it all up in a few more lines. In this tutorial, you learned what GraphQL is - a new age Query Language that is data specific and client-oriented, how is it different (and better) than REST architecture - it is developer friendly, blazing-fast, and easy to learn or understand. We also made a mock API of Movies using GraphQL and MongoDB and performed the CRUD operations using just one single endpoint URL - another benefit over the RESTful architecture. And finally, you went on to create a React application that uses these benefits of GraphQL and combines them with the benefits of React to give a hyper-fast, easy, and full-stack app that renders Movies on request.We hope you learned something new from this article. Once you’ve started this journey of GraphQL, it is a fun ride ahead since it is a relatively new tech and not many people out there are having this skill under their hood. So, make use of this opportunity and outshine the rest.Keep Learning.
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Create GraphQL API with example

Recently, GraphQL has made a lot of buzz among the... Read More

How to use Timers in Node.js

You can use Node.js's utilities to schedule the execution of your code. The timer module, unlike most Node.js modules, is not imported. To comply with the JavaScript browser API, the methods are globally accessible.The Node.js Timers module contains several functions that allow you to execute a block of code or a function after a specified amount of time. You don't need to use require() to import the Timers module because it's global.In this post, I'll explain and demonstrate what timers are, how to use them, how the syntax looks, and how you can use them in your applications. For example, if you want to retrieve data from a REST API at a specific interval, you can easily do so with timers. So, even if you are unfamiliar with JavaScript or timers, this post will help you understand these concepts.The Event Loop - A Quick PrimerNode.js is a single-threaded, event-driven platform that can run non-blocking, asynchronous code. These Node.js features make it memory efficient. Even though JavaScript is single-threaded, the event loop enables Node.js to perform non-blocking I/O operations. It is accomplished by delegating tasks to the operating system whenever and wherever possible.Because most operating systems are multi-threaded, they can handle multiple operations that are running in the background. When one of these operations is finished, the kernel notifies Node.js, and the callback associated with that operation is added to the event queue, where it will eventually be executed.Features of Event Loop:An event loop is an infinite loop that waits for tasks, executes them, and then sleeps until more tasks are received.When the call stack is empty, i.e., there are no ongoing tasks, the event loop executes tasks from the event queue.We can use callbacks and promises in the event loop.The event loop executes the tasks in reverse order, beginning with the oldest.Example:console.log("One"); setTimeout(function(){ console.log("Two"); }, 1000); console.log("Three");Output:OneThreeTwoThe first console log statement is pushed to the call stack in the above example, and "One" is logged on the console before the task is popped from the stack. Following that, the setTimeout is added to the queue, the task is sent to the operating system, and the task's timer is set. After that, this task is removed from the stack. The third console log statement is then pushed to the call stack, "Three" is logged on the console, and the task is removed from the stack.Timers in JavaScriptA timer is used in JavaScript to execute a task or function at a specific time. The timer is essentially used to delay the execution of the program or to execute the JavaScript code at regular intervals. You can delay the execution of the code by using a timer. As a result, when an event occurs or a page loads, the code does not complete its execution at the same time.Advertisement banners on websites, which change every 2-3 seconds, are the best example of a timer. These advertising banners are rotated at regular intervals on websites such as Flipkart. To change them, you set a time interval.JavaScript provides two timer functions, setInterval() and setTimeout(), which help to delay code execution and allow one or more operations to be performed repeatedly.setTimeout():The setTimeout() function allows users to postpone the execution of code. The setTimeout() method accepts two parameters, one of which is a user-defined function, and the other is a time parameter to delay execution. The time parameter, which is optional to pass, stores the time in milliseconds (1 second = 1000 milliseconds).setInterval():The setInterval method is similar to the setTimeout() function in some ways. It repeats the specified function after a time interval. Alternatively, you can say that a function is executed repeatedly after a certain amount of time specified by the user in this function.Timers in Node.js - setTimeout()setTimeout() can be used to execute code after a specified number of milliseconds. This function is equivalent to window. setTimeout() from the browser JavaScript API, but no code string can be passed to be executed.setTimeout() takes a function to execute as the first argument and a millisecond delay defined as a number as the second. Additional arguments may be provided, and these will be passed to the function. As an example, consider the following:Using setTimeout()The timeout interval is not guaranteed to execute after that exact number of milliseconds. This is because any other code that blocks or holds onto the event loop will delay the execution of the timeout. The only guarantee is that the timeout will not be executed sooner than the timeout interval specified.setTimeout(function A() { return console.log('Hello World!'); }, 2000); console.log('Executed before A');clearTimeout():The clearTimeout() method deactivates a timer that was previously set with the setTimeout() method.The ID value returned by setTimeout() is passed to the clearTimeout() method as a parameter.Syntax:clearTimeout(id_of_settimeout)Example: function welcome () { console.log("Welcome to Knowledgehut!"); } var id1 = setTimeout(welcome,1000); var id2 = setInterval(welcome,1000); clearTimeout(id1);Timers in Node.js - setImmediate()To execute code at the end of the loop cycle, use the setImmediate() method. In layman's terms, this method divides tasks that take longer to complete, in order to run a callback function that is triggered by other operations such as events.Syntax:let immediateId = setImmediate(callbackFunction, [param1, param2, ...]); let immediateId = setImmediate(callbackFunction);The function to be executed will be the first argument to setImmediate(). When the function is executed, any additional arguments will be passed to it.Now consider the difference between setImmediate() and process. nextTick(), as well as when to use which.While processing, setImmediate() is executed in the Check handlers phase. process.nextTick() is called at the start of the event loop and at the end of each phase.process.nextTick() has higher priority than setImmediate():setImmediate(() => console.log('I run immediately')) process.nextTick(() => console.log('But I run before that'))Output:Using setImmediate()Multiple setImmediate functions are called in the following example. When you do this, the callback functions are queued for execution in the order in which they are created. After each event loop iteration, the entire callback queue is processed. If an immediate timer is queued from within an executing callback, it will not be triggered until the next iteration of the event loop.Example:setImmediate(function A() { setImmediate(function B() { console.log(1); setImmediate(function D() {   console.log(2); }); }); setImmediate(function C() { console.log(3); setImmediate(function E() {   console.log(4); }); }); }); console.log('Started');clearImmediate():The clearImmediate function is used to remove the function call that was scheduled by the setImmediate function. Both of these functions can be found in Node.js's Timers module.Example:console.log("Before the setImmediate call") let timerID = setImmediate(() => {console.log("Hello, World")}); console.log("After the setImmediate call") clearImmediate(timerID);Timers in Node.js - setInterval()This method, unlike setTimeout(), is used to execute code multiple times. For example, the company may send out weekly newsletters to its Edge as a Service customer. This is where the setInterval() method comes into play. It is an infinite loop that will continue to execute as long as it is not terminated (or halted).As the second argument, setInterval() accepts a function argument that will run an infinite number of times with a given millisecond delay. In the same way that setTimeout() accepts additional arguments beyond the delay, these will be passed on to the function call. The delay, like setTimeout(), cannot be guaranteed due to operations that may stay in the event loop and should thus be treated as an approximation.Syntax:let intervalId = setInterval(callbackFunction, [delay, argument1, argument2, ...]); //option 1 let intervalId = setInterval(callbackFunction[, delayDuration]); // option 2 let intervalId = setInterval(code, [delayDuration]); //option 3Using setInterval()Example:setInterval(function A() { return console.log('Hello World!'); }, 1000); // Executed right away console.log('Executed before A');setInterval(), like setTimeout() returns a Timeout object that can be used to reference and modify the interval that was set.In the above example, function A() will execute after every 1000 milliseconds.clearInterval():Example:var si = setInterval(function A() { return console.log("Hello World!"); }, 1000); setTimeout(function() { clearInterval(si); }, 4000);Using Timer.unref()The timer module is used to schedule functions that will be called later. Because it is a global API, there is no need to import (require("timers")) to use it.The Timeout Class contains an object (setTimeout()/setInterval()) that is created internally to schedule actions, and (clearTimeout()/clearInterval()) that can be passed to cancel those scheduled actions. When a timeout is set, the Node.js event loop will continue to run until clearTimeout() is called. The setTimeout() method returns timeout objects that can be used to control this default behaviour, and it exports both the timeout.ref() and timeout.unref() functions.timeout.ref():When the Timeout is active and (timeout.ref()) is called, it requests that the Node.js event loop not exit for an extended period of time. In any case, calling this Method multiple times has no effect.Syntax:timeout.ref()timeout.unref():When the Timeout is enabled, the Node.js event loop is not required to remain active. If any other activity keeps the event loop running, the Timeout object's callback is invoked after the process exits. In any case, calling this Method multiple times has no effect.Syntax:timeout.unref()Example:var Timeout = setTimeout(function alfa() { console.log("0.> Setting Timeout", 12); }); console.log("1 =>", Timeout.ref()); Timeout.unref() Timeout.ref() console.log("2 =>", Timeout.unref()); clearTimeout(Timeout); console.log("3 => Printing after clearing Timeout"); Output:Scheduling Made SimplerIn this tutorial, you learned how to schedule tasks with the Node.js timer module. You've seen how to set timeouts, interval timers for recurring tasks, and how to use set immediate to bypass long operations. You've also seen how to stop these operations using the clear() method for each method.As with learning anything new, practising what you learn will make a big difference to how easily you can perform these tasks. Share your thoughts and questions in the comments as you try out what you’ve learnt.
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How to use Timers in Node.js

You can use Node.js's utilities to schedule the ex... Read More