The while loop in JavaScript

While writing a program, you may encounter a situation where you need to perform an iterative action. In these situations, you will need to write loop commands to reduce the number of lines of code.

JavaScript supports all the necessary loops to reduce the pressure of the program:

While loop

The most basic loop in JavaScript is the while loop that will be discussed in this chapter. The purpose of the while loop is to execute a command or repeated code block as long as the expression - the expression is true . Once the expression becomes false , the loop ends.

Implementation diagram

The diagram showing the while loop implementation process is as follows:

The while loop in JavaScript Picture 1

Syntax

The following is the while loop syntax in JavaScript:

 while ( expression ){ Statement ( s ) to be executed if expression is true }

For example

You try the following example to execute a while loop.

  type = "text/javascript" >

 Set the variable to different value and then try.

Result:

 Starting Loop 
 Current Count: 0 
 Current Count: 1 
 Current Count: 2 
 Current Count: 3 
 Current Count: 4 
 Current Count: 5 
 Current Count: 6 
 Current Count: 7 
 Current Count: 8 
 Current Count: 9 
 Loop stopped! 
 Đặt biến vào giá trị khác nhau và thử thử .

Do . while loop

The do . while loop is similar to the while loop except that the condition check occurs at the end of the loop. This means that the loop will always be executed at least once, even if the condition is false .

Implementation diagram

Here is the do-while loop implementation diagram:

The while loop in JavaScript Picture 2

Syntax

Do . while loop syntax in JavaScript is as follows:

 do { Statement ( s ) to be executed ; } while ( expression );

Note - Don't forget the semicolon used at the end of the do . while loop.

For example

Try the following example to learn how to execute a do . while loop in JavaScript.

  type = "text/javascript" >

 Set the variable to different value and then try.

Result:

 Starting Loop 
 Current Count: 0 
 Current Count: 1 
 Current Count: 2 
 Current Count: 3 
 Current Count: 4 
 Loop Stopped! 
 Đặt biến vào giá trị khác nhau và thử thử .

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while loop while loop in JavaScript

Lesley Montoya

Update 25 May 2019

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