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Installation of Angular on Ubuntu

Angular is an Open source and TypeScript-based modern framework which is usually used to develop Front end Single Page Applications (SPAs) and PWAs. Angular is the updated version of AngularJS by the same team at Google.  With respect to programming, there is a huge difference in both versions. AngularJS is commonly used with JavaScript whereas Angular is mostly used with TypeScript. This article helps you to summarize on how you can install Angular CLI on your Ubuntu platform and use it to create real-life Angular Applications / Projects. This blog will cover the process steps of Angular installation on the Ubuntu platform. By the end of the blog, you will learn about - Installing Node/npm package on Ubuntu Installation and Usage of Angular CLI globally Commands of Angular CLI Creating an initial workspace for the application Running the Angular application in BrowserPre-requisites You must be aware of the basics of web programming like HTML, CSS, and JavaScript. (otherwise we strongly recommend learning those first before getting into this). Also, this article assumes that you are familiar with terms like Node/NPM. Audience This document can be referred by anyone who wants to install latest Angular version on Ubuntu 16.04. In order to continue, you must have —  System requirementsUbuntu OS Machine Good Internet Connection Admin/Sudo access with installation privileges where you can install any packages freely. PS: While working with Angular, knowledge of TypeScript is good to have, but not mandatoryA brief note on Node.js We are required to install Node.js because it acts as a lightweight server to run Angular applications. (If already installed, skip this part and jump to the next part of this blog.) Node.js is again an open-source and cross-platform JavaScript run-time environment that allows to execute the JavaScript code outside of a browser (on the Server-side). Node.js is responsible for managing and installing all npm dependencies for your Angular application. It provides all the required libraries to run the Angular project. Node.js acts as a run-time environment for any Angular application with servers over localhost. For more information on Node.js refer the official docs. Any Angular application requires the latest/stable version of Node.js in order to continue. Go to the official website in order to learn more about how to install Node.js on your Ubuntu OS machine. There is more than one way to install Node.js on Ubuntu. You can install it via command line, via PPA (personal package archive), or via NVM (which is Node.js Version Manager) You can install any version current or latest stable version as per your need. In this blog, we learn how to install using Command-Line with the below given commands: curl -sL | sudo -E bash - here setup_12.x is the version, and this command will add the node resource repo into your Ubuntu OS. Now, let’s install Node.js using apt command, by running the below command —  $ sudo apt install nodejs Once installed completely, you can verify that the Node.js and npm versions are installed by using the following command in a terminal/console window. — node -v or node — — version  npm -v 1. Need of NPM for Angular development Node.js serves as the Run-time environment for the application. Similarly, NPM(node package manager) is used as a dependency management tool for any JavaScript application. NPM will allow us to install the libraries required for any Angular application; for example, jQuery, angular-router, angular-http, bootstrap, and many more. You can explore a number of packages available in the npm store here. Note: Once you have installed Node.js it will automatically install NPM on your machine. You can check the version installed using the below command. npm -v 2. Angular CLI — What it is and the complete Installation guideIn the initial days of Angular, developers used to create whole architecture, webpack files, build process, etc for any project on their own from scratch, which is quite a time-consuming and lengthy process. To make it easier for the developer, the Angular team come up with an easy-to-use tool Angular CLI. As the name suggests CLI (command line interface), provides a user (developer) friendly interface where you can run commands to make your development life easier and faster. Angular CLI comes with a number of commands from creating a new project, to creating components, creating a routing configuration file, services, and many more.3. How to Install Angular CLI on Ubuntu To install the Angular CLI on your machine, open the terminal window and run the following command: npm install -g @angular/cli where -g denotes that CLI is being installed globally to your machine, which means you can create or run any command of CLI anywhere on your machine. Once you run the above command CLI will be installed on your machine, and you can verify the version installed using the following command: ng -vIn case you want to install some specific version of Angular CLI, you can run the below command —  npm install -g @angular/cli@x where `x` represents the Version number. You can change it to any valid version number. For more commands of Angular CLI, you can refer to this blog which contains a number of commands to use.4. Create Project using Angular CLI – Hello WORLD Moving on, let’s create our first ever Angular project using Angular CLI. Open your terminal window and type the command below on your machine. ng new hello-worldHere ng is our CLI prefix. new denotes the new project we are creating and hello-world is our project name. You can choose any name you want. After running this command, you will find the full architecture of the project in the directory where you run this command. The project folder will be like what is shown below -5. Angular Project architecture The first file to render on running this application will be index.html which is present in the src folder. src folder contains Source files for the root-level application project. assets folder contains all the static assets like images, fonts, etc. node_modules This folder is created while you run npm installed by package manager (npm) and it contains all the project dependencies or any third party modules required for the project. e2e folder contains all the source code related to Test Cases, and you can customize it as per your requirements. README.md file is being used as documentation for the app. Package.json configures npm dependencies that are available to the project in the workspace along with their versions specified. For more details about components/services and source code you can explore this link. Run the application You have completed the installation process of the Angular application via CLI, and now it’s time to run the application locally. As I said, Angular CLI comes with a complete tool-chain/commands for the development of front-end applications on your machine. Run the following command on the terminal (Navigate to the project directory if you are not in that directory) ng serve or ng serve --openThe --open (or just -o) option automatically opens your browser to  ng serve command will serve your application on localhost server which you can check by navigating to your browser with the below URL Once compiled successfully, your terminal window will look like below -You can customize the port as per your requirement by running the below command —  ng serve --host 0.0.0.0 --port 8080 Accessing Angular Web Interface ng serve command may take few seconds to run your application. Once completed, you should see a web page similar to the followingAnd it’s done! Now you can make changes in the default component’s template which is app.component.html  Also, moving forward you can generate a number of components/service/routing files using CLI commands as per your requirements and keep learning. 6. How to Uninstall Angular CLI on Ubuntu There are cases when you would need to uninstall Angular-CLI from your operating system. You can do so by running this below command on your terminal -  npm uninstall -g @angular/cli It's always recommended to run the command npm cache clean after uninstallation of Angular CLI from your system in order to avoid unwanted errors while installing it again. If you have any questions/doubts related to this blog, please let us know in the comment box below, and we would be more than happy to help you out.  If you have read this far, feel free to share this blog on social media or tweet about it.  Conclusion In this blog you have learned about what is Node/NPM and how you can install and use it. You have understood what is Angular CLI, and how you can use it after installing it on your Ubuntu Platform. Then we have created a new angular project from scratch using CLI command, and learnt how to run it. Now you have basic hands-on Angular application knowledge which you can use to start developing more applications. 

Installation of Angular on Ubuntu

6K
  • by Pardeep Jain
  • 17th Apr, 2021
  • Last updated on 20th Apr, 2021
  • 7 mins read
Installation of Angular on Ubuntu

Angular is an Open source and TypeScript-based modern framework which is usually used to develop Front end Single Page Applications (SPAs) and PWAs. Angular is the updated version of AngularJS by the same team at Google.  

With respect to programming, there is a huge difference in both versions. AngularJS is commonly used with JavaScript whereas Angular is mostly used with TypeScript. 

This article helps you to summarize on how you can install Angular CLI on your Ubuntu platform and use it to create real-life Angular Applications / Projects. 

This blog will cover the process steps of Angular installation on the Ubuntu platform. By the end of the blog, you will learn about - 

  • Installing Node/npm package on Ubuntu 
  • Installation and Usage of Angular CLI globally 
  • Commands of Angular CLI 
  • Creating an initial workspace for the application 
  • Running the Angular application in Browser

Pre-requisites 

You must be aware of the basics of web programming like HTML, CSS, and JavaScript(otherwise we strongly recommend learning those first before getting into this). Also, this article assumes that you are familiar with terms like Node/NPM. 

Audience 

This document can be referred by anyone who wants to install latest Angular version on Ubuntu 16.04. 

In order to continue, you must have —  

System requirements

  • Ubuntu OS Machine 
  • Good Internet Connection 
  • Admin/Sudo access with installation privileges where you can install any packages freely. 

PS: While working with Angular, knowledge of TypeScript is good to have, but not mandatory

A brief note on Node.js 

We are required to install Node.js because it acts as a lightweight server to run Angular applications. (If already installed, skip this part and jump to the next part of this blog.) 

Node.js is again an open-source and cross-platform JavaScript run-time environment that allows to execute the JavaScript code outside of a browser (on the Server-side). Node.js is responsible for managing and installing all npm dependencies for your Angular application. It provides all the required libraries to run the Angular project. Node.js acts as a run-time environment for any Angular application with servers over localhost. For more information on Node.js refer the official docs. 

Any Angular application requires the latest/stable version of Node.js in order to continue. Go to the official website in order to learn more about how to install Node.js on your Ubuntu OS machine. 

There is more than one way to install Node.js on Ubuntu. You can install it via command line, via PPA (personal package archive), or via NVM (which is Node.js Version Manager) 

You can install any version current or latest stable version as per your need. In this blog, we learn how to install using Command-Line with the below given commands: 

curl -sL sudo -E bash - 

here setup_12.x is the version, and this command will add the node resource repo into your Ubuntu OS. Now, let’s install Node.js using apt command, by running the below command —  

sudo apt install nodejs 

Once installed completely, you can verify that the Node.js and npm versions are installed by using the following command in a terminal/console window. — 

node -v 

or 

node — — version 
npm -v 

1. Need of NPM for Angular development 

Node.js serves as the Run-time environment for the applicationSimilarly, NPM(node package manager) is used as a dependency management tool for any JavaScript application. NPM will allow us to install the libraries required for any Angular application; for example, jQuery, angular-router, angular-http, bootstrap, and many more. 

You can explore a number of packages available in the npm store here. 

Note: Once you have installed Node.js it will automatically install NPM on your machine. You can check the version installed using the below command. 

npm -v 

2. Angular CLI — What it is and the complete Installation guide

In the initial days of Angular, developers used to create whole architecture, webpack files, build process, etc for any project on their own from scratch, which is quite a time-consuming and lengthy process. To make it easier for the developer, the Angular team come up with an easy-to-use tool Angular CLI. 

As the name suggests CLI (command line interface), provides a user (developer) friendly interface where you can run commands to make your development life easier and faster. 

Angular CLI comes with a number of commands from creating a new project, to creating components, creating a routing configuration file, services, and many more.

3. How to Install Angular CLI on Ubuntu 

To install the Angular CLI on your machine, open the terminal window and run the following command: 

npm install -g @angular/cli 

where -g denotes that CLI is being installed globally to your machine, which means you can create or run any command of CLI anywhere on your machine. Once you run the above command CLI will be installed on your machine, and you can verify the version installed using the following command: 

ng -v

In case you want to install some specific version of Angular CLI, you can run the below command —  

npm install -g @angular/cli@x 

where `x` represents the Version number. You can change it to any valid version number. 

For more commands of Angular CLI, you can refer to this blog which contains a number of commands to use.

4. Create Project using Angular CLI – Hello WORLD 

Moving on, let’s create our first ever Angular project using Angular CLI. Open your terminal window and type the command below on your machine. 

ng new hello-world

Here ng is our CLI prefixnew denotes the new project we are creating and hello-world is our project name. You can choose any name you want. 

After running this command, you will find the full architecture of the project in the directory where you run this command. The project folder will be like what is shown below -Installation of Angular on Ubuntu

5. Angular Project architecture 

The first file to render on running this application will be index.html which is present in the src folder. 

  • src folder contains Source files for the root-level application project. 
  • assets folder contains all the static assets like images, fonts, etc. 
  • node_modules This folder is created while you run npm installed by package manager (npm) and it contains all the project dependencies or any third party modules required for the project. 
  • e2e folder contains all the source code related to Test Cases, and you can customize it as per your requirements. 
  • README.md file is being used as documentation for the app. 
  • Package.json configures npm dependencies that are available to the project in the workspace along with their versions specified. 

For more details about components/services and source code you can explore this link. 

Run the application 

You have completed the installation process of the Angular application via CLI, and now its time to run the application locally. As I said, Angular CLI comes with a complete tool-chain/commands for the development of front-end applications on your machine. 

Run the following command on the terminal (Navigate to the project directory if you are not in that directory) 

ng serve 

or 

ng serve --open

The --open (or just -o) option automatically opens your browser to  

ng serve command will serve your application on localhost server which you can check by navigating to your browser with the below URL

Once compiled successfully, your terminal window will look like below -Installation of Angular on Ubuntu

You can customize the port as per your requirement by running the below command —  

ng serve --host 0.0.0.0 --port 8080 

Accessing Angular Web Interface 

ng serve command may take few seconds to run your application. Once completed, you should see a web page similar to the following

ng serve command

And it’s done! 

Now you can make changes in the default component’s template which is app.component.html  

Also, moving forward you can generate number of components/service/routing files using CLI commands as per your requirements and keep learning. 

6. How to Uninstall Angular CLI on Ubuntu 

There are cases when you would need to uninstall Angular-CLI from your operating system. You can do so by running this below command on your terminal -  

npm uninstall -g @angular/cli 

It's always recommended to run the command npm cache clean after uninstallation of Angular CLI from your system in order to avoid unwanted errors while installing it again. If you have any questions/doubts related to this blog, please let us know in the comment box below, and we would be more than happy to help you out.  If you have read this far, feel free to share this blog on social media or tweet about it.  

Conclusion 

In this blog you have learned about what is Node/NPM and how you can install and use it. You have understood what is Angular CLI, and how you can use it after installing it on your Ubuntu Platform. Then we have created a new angular project from scratch using CLI command, and learnt how to run it. Now you have basic hands-on Angular application knowledge which you can use to start developing more applications. 

Pardeep

Pardeep Jain

Author

Pardeep having 6 Years of experience in the IT Industry, He loves to write Blogs along with Open source contributions on StackOverflow, Github, etc. He majorly works on advanced Frontend frameworks/Libraries like Angular, React, Amazon Alexa skills, etc.

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For example, instead of using onClick, use onClickCapture to handle the click event.  Capture event example:                  Click me    Additional ExamplesExample1                       Import React from ‘...react’                         function clickAppHandler() {                                function clickHandler() {                                        console.log(‘clicked’)                                         }                                  return (                                                                                  Click                                                                          )                         }                       export default clickAppHandler   Example2       This example is along with HTML in a single file                                                            Events                               function testApp (){                        alert((“Hello Event”);                                                   test Clicked                  test double Clicked                     Adding Events: Below example is how you add an event. Highlighted in bold                      Import React from ‘...react’                         function clickAppHandler() {                                function clickHandler() {                                        console.log(‘clicked’)                                         }                                  return (                                                                                  Click                                                                          )                         }                       export default clickAppHandler  Passing Arguments to Event HandlerThere are two ways arguments are passed to event handler  Arrow function                    this.handleClick(id,e)}>Click                onClick is the event                e is the event object                 id can be state or props or some data Bind method      Click  In this case event object is automatically passed In both methods e represents the react event and its passed after the ID as second argument,With an arrow function this event e is passed explicitly but with bind method its automatically passed.                                     Import React,{ Component } from “react”;                                         class TestApp extends Component {                                           state = {                                                       id: 2,                                                      Name: “TestApp Dummy”                                                };                                                             //arrow function                                                 handleClick = (id,e) => {                                                       console.log(id);                                                       console.log(e);                                                  };                                               handleArg = (e) => { this.handleClick(this.state.id,e);}                                                          render() {     return (                    TestApp,{this.state.name}            onClick={this.handleArg}>Display            );   }  }  The react event is an object and obtained from react. Instead of creating a separate function for passing argument, you can directly pass the anonymous arrow function as shown in the render function below:     render() {        return (                                                                                                       TestApp,{this.state.name}                                                {                           this.handleClick(this.state.id,e);                                                               }}>Display                                                                                                         );                                                 }                                            }    Output:   click on button  “TestApp Dummy “                   Let’s see only how bind method looks like in the render function    render() {                                         return (                                                                                                 TestApp,{this.state.name}                                                   Display                                                                                                       );                                                  }                                              } Output: this will display the h1 tag and when you click the button handleClick function gets invoked and the console will display id of the state object as shown above. Building a Practice to Thoroughly Understand Events This blog focuses on event handling, which in turn teaches about event handlers declared in JSX markup.This approach helps in tracking down the element mapped with events in an easy way.  We also learned how to handle multiple event handlers in a single element by using JSX attributes.we also learned about ways to bind event handler and  parameter values. Then we learned about synthetic events which are abstractions around native events. The best way you can retain this learning is by practicing more and tackling the complexities that may arise as you practice. You can find several tutorials on the internet or share your questions with us here. Happy learning! 
5355
Handling React Events - A Detailed Guide

Event handling essentially allows the user to inte... Read More

MongoDB Query Document Using Find() With Example

MongoDB's find() method selects documents from a collection or view and returns a cursor to those documents. There are two parameters in this formula: query and projection.Query – This is an optional parameter that specifies the criteria for selection. In simple terms, a query is what you want to search for within a collection.Projection – This is an optional parameter that specifies what should be returned if the query criteria are satisfied. In simple terms, it is a type of decision-making that is based on a set of criteria.MongoDB's Flexible SchemaA NoSQL database, which stands for "not only SQL," is a way of storing and retrieving data that is different from relational databases' traditional table structures (RDBMS).When storing large amounts of unstructured data with changing schemas, NoSQL databases are indeed a better option than RDBMS. Horizontal scaling properties of NoSQL databases allow them to store and process large amounts of data.These are intended for storing, retrieving, and managing document-oriented data, which is frequently stored in JSON format (JavaScript Object Notation). Document databases, unlike RDBMSs, have a flexible schema that is defined by the contents of the documents.MongoDB is one of the most widely used open-source NoSQL document databases. MongoDB is known as a 'schemaless' database because it does not impose a specific structure on documents in a collection.MongoDB is compatible with a number of popular programming languages. It also offers a high level of operational flexibility because it scales well horizontally, allowing data to be spread or 'sharded' across multiple commodity servers with the ability to add more servers as needed. MongoDB can be run on a variety of platforms, including developer laptops, private clouds, and public clouds.Querying documents using find()MongoDB queries are used to retrieve or fetch data from a MongoDB database. When running a query, you can use criteria or conditions to retrieve specific data from the database.The function db.collection is provided by MongoDB. find() is a function that retrieves documents from a MongoDB database.In MongoDB, the find method is used to retrieve a specific document from the MongoDB collection. In Mongo DB, there are a total of six methods for retrieving specific records.find()findAndModify()findOne()findOneAndDelete()findOneAndReplace()findOneAndUpdate()Syntax:find(query, projection)We can fetch a specific record using the Find method, which has two parameters. If these two parameters are omitted, the find method will return all of the documents in the MongoDB collection.Example:Consider an example of employees with the database of employee_id and employee_name and we will fetch the documents using find() method.First, create a database with the name “employees” with the following code:use employeesNow, create a collection “employee” with:db.createCollection("employee")In the next step we will insert the documents in the database:db.employee.insert([{employee_id: 101, employee_name: "Ishan"}, {employee_id: 102, employee_name: "Bhavesh"}, {employee_id: 103, employee_name: "Madan"}])Find all Documents:To get all the records in a collection, we need to use the find method with an empty parameter. In other words, when we need all the records, we will not use any parameters.db.employee.find()Output in Mongo ShellThe pretty() method can be used to display the results in a formatted manner.Syntax:db.COLLECTION_NAME.find().pretty()Let’s check our documents with pretty() method:Query FiltersWe will see examples of query operations using the db.collection.find() method in mongosh.We will use the employee collection in the employees database.db.employee.insert([{employee_id: 101, employee_name: "Ishan", age: 21, email_id: "ishanjain@gmail.com"}, {employee_id: 102, employee_name: "Bhavesh", age: 22, email_id: "bhaveshg@gmail.com"}, {employee_id: 103, employee_name: "Madan", age: 23, email_id: "madan@gmail.com"}])As we have seen earlier that to select all the documents in the database we pass an empty document as the query filter parameter to the find method.db.employee.find().pretty()Find the first document in a collection:db.employee.findOne()Find a document by ID:db.employee.findOne({_id : ObjectId("61d1ae0b56b92c20b423a5a7")})Find Documents that Match Query Criteriadb.employee.find({“age”: “22”})db.employee.find({"employee_name": "Madan"}).pretty()Sort Results by a Field:db.employee.find().sort({age: 1}).pretty()order by age, in ascending orderdb.employee.find().sort({age: -1}).pretty()order by age, in descending orderAND Conditions:A compound query can specify conditions for multiple fields in the documents in a collection. A logical AND conjunction connects the clauses of a compound query indirectly, allowing the query to select all documents in the collection that meet the specified conditions.In the following example, we will consider all the documents in the employee collection where employee_id equals 101 and age equals 21.db.employee.find({"employee_id": 101, "age": "21" }).pretty()Querying nested fieldsThe embedded or nested document feature in MongoDB is a useful feature. Embedded documents, also known as nested documents, are documents that contain other documents.You can simply embed a document inside another document in MongoDB. Documents are defined in the mongo shell using curly braces (), and field-value pairs are contained within these curly braces.Using curly braces, we can now embed or set another document inside these fields, which can include field-value pairs or another sub-document.Syntax:{ field: { field1: value1, field2: value2 } }Example:We have a database “nested” and in this database we have collection “nesteddoc”.The following documents will insert into the nesteddoc collection.db.nesteddoc.insertMany([ { "_id" : 1, "dept" : "A", "item" : { "sku" : "101", "color" : "red" }, "sizes" : [ "S", "M" ] }, { "_id" : 2, "dept" : "A", "item" : { "sku" : "102", "color" : "blue" }, "sizes" : [ "M", "L" ] }, { "_id" : 3, "dept" : "B", "item" : { "sku" : "103", "color" : "blue" }, "sizes" : "S" }, { "_id" : 4, "dept" : "A", "item" : { "sku" : "104", "color" : "black" }, "sizes" : [ "S" ] } ])Place the documents in the collection now. Also, take a look at the results:As a result, the nesteddoc collection contains four documents, each of which contains nested documents. The find() method can be used to access the collection's documents.db.nesteddoc.find()Specify Equality Condition:In this example, we will select the document from the nesteddoc query where dept equals “A”.db.nesteddoc.find({dept: "A"})Querying ArraysUse the query document {: } to specify an equality condition on an array, where is the exact array to match, including the order of the elements.The following query looks for all documents where the field tags value is an array with exactly two elements, "S" and "M," in the order specified:db.nesteddoc.find( { sizes: ["S", "M"] } )Use the $all operator to find an array that contains both the elements "S" and "M," regardless of order or other elements in the array:db.nested.find( { sizes: { $all: ["S", "M"] } } )Query an Array for an Element:The following example queries for all documents where size is an array that contains the string “S” as one of its elements:db.nesteddoc.find( { sizes: "S" } )Filter conditionsTo discuss the filter conditions, we will consider a situation that elaborates this. We will start by creating a collection with the name “products” and then add the documents to it.db.products.insertMany([ { _id: 1, item: { name: "ab", code: "123" }, qty: 15, tags: [ "A", "B", "C" ] }, { _id: 2, item: { name: "cd", code: "123" }, qty: 20, tags: [ "B" ] }, { _id: 3, item: { name: "ij", code: "456" }, qty: 25, tags: [ "A", "B" ] }, { _id: 4, item: { name: "xy", code: "456" }, qty: 30, tags: [ "B", "A" ] }, { _id: 5, item: { name: "mn", code: "000" }, qty: 20, tags: [ [ "A", "B" ], "C" ] }])To check the documents, use db.products.find():$gt$gt selects documents with a field value greater than (or equal to) the specified value.db.products.find( { qty: { $gt: “20” } } )$gte:$gte finds documents in which a field's value is greater than or equal to (i.e. >=) a specified value (e.g. value.)db.products.find( { qty: { $gte: 20 } } )$lt:$lt selects documents whose field value is less than (or equal to) the specified value.db.products.find( { qty: { $lt: 25 } } )$lte:$lte selects documents in which the field's value is less than or equal to (i.e. =) the specified value.db.products.find( { qty: { $lte: 20 } } )Query an Array by Array Length:To find arrays with a specific number of elements, use the $size operator. For example, the following selects documents with two elements in the array.db.products.find( { "tags": {$size: 2} } )ProjectionIn MongoDB, projection refers to selecting only the data that is required rather than the entire document's data. If a document has five fields and you only want to show three of them, select only three of them.The find() method in MongoDB accepts a second optional parameter, which is a list of fields to retrieve, as explained in MongoDB Query Document. When you use the find() method in MongoDB, it displays all of a document's fields. To prevent this, create a list of fields with the values 1 or 0. The value 1 indicates that the field should be visible, while 0 indicates that it should be hidden.Syntax:db.COLLECTION_NAME.find({},{KEY:1})Example:We will consider the previous example of products collection. Run the below command on mongoshell to learn how projection works:db.products.find({},{"tags":1, _id:0})Keep in mind that the _id field is always displayed while executing the find() method; if you do not want this field to be displayed, set it to 0.Optimized FindingsTo retrieve a document from a MongoDB collection, use the Find method.Using the Find method, we can retrieve specific documents as well as the fields that we require. Other find methods can also be used to retrieve specific documents based on our needs.By inserting array elements into the query, we can retrieve specific elements or documents. To retrieve data for array elements from the collection in MongoDB, we can use multiple query operators.
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MongoDB Query Document Using Find() With Example

MongoDB's find() method selects documents from a c... Read More

Implementing MongoDb Map Reduce using Aggregation

Algorithms and applications in today's data-driven market collect data about people, processes, systems, and organisations 24 hours a day, seven days a week, resulting in massive amounts of data. The problem is figuring out how to process this massive amount of data efficiently without sacrificing valuable insights.What is Map Reduce? The MapReduce programming model comes to the rescue here. MapReduce, which was first used by Google to analyse its search results, has grown in popularity due to its ability to split and process terabytes of data in parallel, generating results faster. A (Key,value) pair is the basic unit of information in MapReduce. Before feeding the data to the MapReduce model, all types of structured and unstructured data must be translated to this basic unit. The MapReduce model, as the name implies, consists of two distinct routines: the Map-function and the Reduce-function.  MapReduce is a framework for handling parallelizable problems across huge files using a huge number of devices (nodes), which are collectively referred to as a cluster (if all nodes are on the same local network and use similar hardware) or a grid (if the nodes are shared across geographically and administratively distributed systems, and use more heterogeneous hardware).  When data stored in a filesystem (unstructured) or a database(structured) is processed, MapReduce can take advantage of data's locality, processing it close to where it's stored to reduce communication costs. Typically, a MapReduce framework (or system) consists of three operations: Map: Each worker node applies the map function to local data and saves the result to a temporary storage. Only one copy of the redundant input data is processed by a master node. Shuffle: worker nodes redistribute data based on output keys (produced by the map function), ensuring that all data associated with a single key is stored on the same worker node. Reduce: each group of output data is now processed in parallel by worker nodes, per key. This article will walk you through the Map-Reduce model's functionality step by step. Map Reduce in MongoDB The map-reduce operation has been deprecated since MongoDB 5.0. An aggregation pipeline outperforms a map-reduce operation in terms of performance and usability. Aggregation pipeline operators like $group, $merge, and others can be used to rewrite map-reduce operations. Starting with version 4.4, MongoDB provides the $accumulator and $function aggregation operators for map-reduce operations that require custom functionality. In JavaScript, use these operators to create custom aggregation expressions. The map and reduce functions are the two main functions here. As a result, the data is independently mapped and reduced in different spaces before being combined in the function and saved to the specified new collection. This mapReduce() function was designed to work with large data sets only. You can perform aggregation operations like max and avg on data using Map Reduce, which is similar to groupBy in SQL. It works independently and in parallel on data. Implementing Map Reduce with Mongosh (MongoDB Shell)  The db.collection.mapReduce() method in mongosh is a wrapper for the mapReduce command. The examples that follow make use of the db.collection.mapReduce(). Example: Create a collection ‘orders’ with these documents: db.orders.insertMany([     { _id: 1, cust_id: "Ishan Jain", ord_date: new Date("2021-11-01"), price: 25, items: [ { sku: "oranges", qty: 5, price: 2.5 }, { sku: "apples", qty: 5, price: 2.5 } ], status: "A" },     { _id: 2, cust_id: "Ishan Jain", ord_date: new Date("2021-11-08"), price: 70, items: [ { sku: "oranges", qty: 8, price: 2.5 }, { sku: "chocolates", qty: 5, price: 10 } ], status: "A" },     { _id: 3, cust_id: "Bhavesh Galav", ord_date: new Date("2021-11-08"), price: 50, items: [ { sku: "oranges", qty: 10, price: 2.5 }, { sku: "pears", qty: 10, price: 2.5 } ], status: "A" },     { _id: 4, cust_id: "Bhavesh Galav", ord_date: new Date("2021-11-18"), price: 25, items: [ { sku: "oranges", qty: 10, price: 2.5 } ], status: "A" },     { _id: 5, cust_id: "Bhavesh Galav", ord_date: new Date("2021-11-19"), price: 50, items: [ { sku: "chocolates", qty: 5, price: 10 } ], status: "A"},     { _id: 6, cust_id: "Madan Parmar", ord_date: new Date("2021-11-19"), price: 35, items: [ { sku: "carrots", qty: 10, price: 1.0 }, { sku: "apples", qty: 10, price: 2.5 } ], status: "A" },     { _id: 7, cust_id: "Madan Parmar", ord_date: new Date("2021-11-20"), price: 25, items: [ { sku: "oranges", qty: 10, price: 2.5 } ], status: "A" },     { _id: 8, cust_id: "Abhresh", ord_date: new Date("2021-11-20"), price: 75, items: [ { sku: "chocolates", qty: 5, price: 10 }, { sku: "apples", qty: 10, price: 2.5 } ], status: "A" },     { _id: 9, cust_id: "Abhresh", ord_date: new Date("2021-11-20"), price: 55, items: [ { sku: "carrots", qty: 5, price: 1.0 }, { sku: "apples", qty: 10, price: 2.5 }, { sku: "oranges", qty: 10, price: 2.5 } ], status: "A" },     { _id: 10, cust_id: "Abhresh", ord_date: new Date("2021-11-23"), price: 25, items: [ { sku: "oranges", qty: 10, price: 2.5 } ], status: "A" }  ]) Apply a map-reduce operation to the orders collection to group them by cust_id, then add the prices for each cust_id: To process each input document, define the map function: this refers the document that the map-reduce operation is processing in the function. For each document, the function maps the price to the cust_id and outputs the cust_id and price. var mapFunction1 = function() {emit(this.cust_id, this.price);}; With the two arguments keyCustId and valuesPrices, define the corresponding reduce function: The elements of the valuesPrices array are the price values emitted by the map function, grouped by keyCustId. The valuesPrice array is reduced to the sum of its elements by this function. var reduceFunction1 = function(keyCustId, valuesPrices) {return Array.sum(valuesPrices);};Apply the mapFunction1 map function and the reduceFunction1 reduce function to all documents in the orders collection: db.orders.mapReduce(mapFunction1,reduceFunction1,{ out: "map_reduce_example" }) The results of this operation are saved in the map_reduce_example collection. If the map_reduce_example collection already exists, the operation will overwrite its contents with the map-reduce operation's results. Check the map_reduce_example collection to verify: db.map_reduce_example.find().sort( { _id: 1 } ) Aggregation Alternative:You can rewrite the map-reduce operation without defining custom functions by using the available aggregation pipeline operators: db.orders.aggregate([{$group: { _id:"$cust_id",value:{$sum: "$price" } } },{ $out: "agg_alternative_1" }]) Check the agg_alternative_1 collection to verify: db.agg_alternative_1.find().sort( { _id: 1 } )Implementing Map Reduce with Java Consider the collection car and insert the following documents in it. db.car.insert( [ {car_id:"c1",name:"Audi",color:"Black",cno:"H110",mfdcountry:"Germany",speed:72,price:11.25}, {car_id:"c2",name:"Polo",color:"White",cno:"H111",mfdcountry:"Japan",speed:65,price:8.5}, {car_id:"c3",name:"Alto",color:"Silver",cno:"H112",mfdcountry:"India",speed:53,price:4.5}, {car_id:"c4",name:"Santro",color:"Grey",cno:"H113",mfdcountry:"Sweden",speed:89,price:3.5} , {car_id:"c5",name:"Zen",color:"Blue",cno:"H114",mfdcountry:"Denmark",speed:94,price:6.5} ] ) You will get an output like this:  Let's now write the map reduce function on a collection of cars, grouping them by speed and classifying them as overspeed cars.  var speedmap = function (){  var criteria;  if ( this.speed > 70 ) {criteria = 'overspeed';emit(criteria,this.speed);}}; Based on the speed, this function classifies the vehicle as an overspeed vehicle. The term "this" refers to the current document that requires map reduction. var avgspeed_reducemap = function(key, speed) {       var total =0;       for (var i = 0; i 
7344
Implementing MongoDb Map Reduce using Aggregation

Algorithms and applications in today's data-driven... Read More