for loop

The Javascript for loop is the most used loop in any programming language. It is because it includes three things which other loops like while have to do in a separate statement.

Any loop like the while loop below have three parts –

var counter = 10; //loop initialization
while(counter > 0) { //test statement
 console.log("Counter is ", counter);
 counter--; //iteration statement
}

Loop initialization

Here we initialize our variable to have an initial value.

Test statement

The statement tests whether our condition is true. We generally check the condition which has some test on the variable declared in above loop initialization.

Iteration statement

A very important part of a loop. It either increment or decrement or loop initialization variable. Generally done from inside the loop and because of it, the loop runs for many times.

Now, in a for loop, we can have all these three steps inside it. We will refactor the while loop to a for a loop.

for(var counter=10; counter > 0 ; counter--) {
 console.log("Counter is ", counter);
}

//Output -

//Counter is 10 
//Counter is 9 
//Counter is 8 
//Counter is 7 
//Counter is 6 
//Counter is 5 
//Counter is 4 
//Counter is 3 
//Counter is 2 
//Counter is 1

Just one thing to keep in mind is that the initialization(var counter=10) is done only once. Then the counter is decremented by 1 and then the test condition(counter > 0) is checked.

This is repeated till counter becomes 0 and the test condition becomes false and we get excited from the loop.