do...while - JavaScript 编辑

The do...while statement 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.

The source for this interactive example is stored in a GitHub repository. If you'd like to contribute to the interactive examples project, please clone https://github.com/mdn/interactive-examples and send us a pull request.

The source for this interactive example is stored in a GitHub repository. If you'd like to contribute to the interactive examples project, please clone https://github.com/mdn/interactive-examples and send us a pull request.

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.

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);

Specifications

Specification
ECMAScript (ECMA-262) The definition of 'do-while statement' in that specification.

Browser compatibility

BCD tables only load in the browser

See also

• while
• for