Until in JavaScript - ECMAScript 2021

The until statement is not a built-in statement in JavaScript. However, you can achieve similar functionality using a while loop together with a negated condition.

The syntax for a while loop is as follows:

while (condition) {
  statement(s)
}

Here, the code inside the while loop will continue to execute as long as the condition is true.

To use until in JavaScript, you can invert the condition and use a while loop. This results in the loop running until the negated condition becomes false.

Here's an example:

let num = 0;
until (num >= 3) {
  console.log(num);
  num++;
}

This code will result in a ReferenceError because until is not a valid statement in JavaScript.

Instead, we can invert the condition and use a while loop like this:

let num = 0;
while (!(num >= 3)) {
  console.log(num);
  num++;
}

Here, the loop will run until num is greater than or equal to 3. The output of this code will be:

0
1
2

Note that this is functionally equivalent to a do-while loop with the condition inside the while clause:

let num = 0;
do {
  console.log(num);
  num++;
} while (num < 3);

This will produce the same output as the previous example:

0
1
2