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do...while

The do...while creates a loop that executes a specified statement until the test condition evaluates to false. The condition is evaluated after executing the statement, resulting in the specified statement executing at least once.

Try it

Syntax

do
  statement
while (condition);
statement

A statement that is executed at least once and is re-executed each time the condition evaluates to true. To execute multiple statements within the loop, use a block statement ({ /* ... */ }) to group those statements.

condition

An expression evaluated after each pass through the loop. If condition evaluates to true, the statement is re-executed. When condition evaluates to false, control passes to the statement following the do...while.

Note: Use the break statement to stop a loop before condition evaluates to true.

Examples

Using do...while

In the following example, the do...while loop iterates at least once and reiterates until i is no longer less than 5.

let result = '';
let i = 0;
do {
  i += 1;
  result += `${i}`;
}
while (i > 0 && i < 5);
// Despite i === 0 this will still loop as it starts off without the test

console.log(result);

Using an assignment as a condition

In some cases, it can make sense to use an assignment as a condition — but when you do, there's a right way to do it, and a wrong way; the while documentation has a Using an assignment as a condition section with an example showing a general best-practice syntax you should know about and follow.

Specifications

Browser compatibility

Desktop Mobile Server
Chrome Edge Firefox Internet Explorer Opera Safari WebView Android Chrome Android Firefox for Android Opera Android Safari on IOS Samsung Internet Deno Node.js
do...while
1
12
1
4
4
1
4.4
18
4
10.1
1
1.0
1.0
0.10.0

See also

© 2005–2022 MDN contributors.
Licensed under the Creative Commons Attribution-ShareAlike License v2.5 or later.
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/do...while