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.

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 false.

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, such as this:

do {
  // …
} while ((match = regexp.exec(str)));

But when you do, there are readability tradeoffs. The while documentation has a Using an assignment as a condition section with our recommendations.

Specifications

Browser compatibility

See also

• while
• for
• break
• continue