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.
do...while
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, thestatement
is re-executed. Whencondition
evaluates to false, control passes to the statement following thedo...while
.Note: Use the
break
statement to stop a loop beforecondition
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.
var result = ''; var 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
|
1
|
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