Learn JavaScript
Loops
14.2
Lesson

while loop

The while loop contains a statement, which is checked at the beginning of each iteration of the loop. If the statement evaluates to true, then the code block runs and the loop moves to its next iteration. If the statement evaluates to false, then the loop terminates immediately and no more code is run.

Let’s look at the example given below, where we print the numbers from 1 to 5 using a while loop.

Here, we first initialize a variable i with the value of 1. We then start a while loop, the steps for which are as follows:

Step 1 - At the beginning of the first iteration, the statement, i < 6 is checked to see if it evaluates to true. Since the current value of i is 1, the statement does evaluate to true.

Step 2 - The code block of the loop is then run, where we print the value of i to the console and increment the value of i by 1.

Step 3 - The loop then moves on to the next iteration, wherein it repeats the steps from Step 1.

Steps 1, 2 and 3 are repeated as long as the statement of the while loop evaluates to true. At one point, the value of i will be 6 at the beginning of an iteration, due to which the statement, i < 6 will evaluate to false. At that point, the loop immediately terminates and no more code is run.