do...while

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.

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);

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.

• while
• for
• break
• continue