While loop in JavaScript; Through this tutorial, you will learn javaScript while loop with the help of syntax, flowchart, and examples.
JavaScript While Loop
- Introduction JavaScript
while
Loop - Syntax of the
while
statement - Flowchart of
while
loop - Example 1: First JavaScript
while
Loop - Example 2: JavaScript
while
Loop with Array
Introduction JavaScript while-loop
The JavaScript while loop is also known as an entry control loop. The JavaScript while
is test specified condition before executing a block of code. If the condition met true, then the block of code will be executed.
Syntax of the while
Loop
while (expression) { // statement }
The while
loop test specified the condition
before execute the block of code.
If the condition
specified condtion met true
, the while
loop executes the block of code
. If the specified condition met false
, execution will be stopped.
You have known above, the while
loop is known as an entry control loop. For this reason, it is possible that the block of code
inside the while
loop is never executed, if the specified condition met false.
Flowchart of while
loop
In the case, if the specified condition is found to be false. And still, you want to execute a block of code at least once. So you should use the do while
Loop.
Example 1: JavaScript while
loop
See the following example that uses the while
loop in javascript:
<script> let count = 1; while (count < 10) { document.write(count + "<br>"); count +=2; } </script>
How the script works:
- First, define
count
variable and assign value to it. - Next, before the first iteration starts, the
while
loop checks specified condition, ifcount
is less than10
and execute the statements inside the loop body. - Next, in each while loop iteration, increments
count
by2
. And After5
iterations, the conditioncount < 10
met false and loop will be terminate.
The output of the script shown below:
1 3 5 7 9
Example 2: JavaScript while
Loop with Array
The following example uses the while
loop to generate 5 random numbers and push into an array.
<script> // create an array empty array let rands = []; // define a count variable and assign value zero to it let count = 0; // define a size variable and assign value 5 to it const size = 5; //test condition while(count < size) { rands.push(Math.round(Math.random() * 10)); count++; console.log('The current size of the array is ' + count); } console.log(rands); </script>
Output:
The current size of the array is 1 The current size of the array is 2 The current size of the array is 3 The current size of the array is 4 The current size of the array is 5 [1, 9, 1, 9, 6]
In this example:
- First, declare and initialize an array.
- Next, define
count and size
variable and assign value to it. - Next, generate a random number by using Math.random() and push it into an array, Inside a loop.
- The
while
loop terminated. When the thecount
equals the value of thesize
variable.
Conclusion
In this tutorial, you have learned how to use the JavaScript while
loop with executed a block of code until the specified condition is met true
.