Break Out of Loop in JavaScript

In JavaScript, the break statement can be used to break out of a loop:

for (let i = 0; i < 10; i++) {
    if (i === 5) {
        break;
    }
    console.log(`Number of times this loop has run: ${i + 1}`);
}

The above loop would run ten times if it weren’t for the break statement which is triggered at the start of the sixth iteration.

So instead, the number of times the loop has been run is printed only five times to the console.

A break statement can be used in a for loop, but not in a forEach loop.

Another common use case for the break statement is in switch block cases.

Nested loop breaking

If you want to break out of a nested loop, you can do so like this:

for (let i = 0; i < 10; i++) {
    for (let j = 0; j < 10; j++) {
        if (j === 5) {
            // Break out of child loop:
            break;
        }
    }
}

The above example will break out of the nested loop when j is 5, returning to the parent loop.

If you want to break out of a parent loop from a nested loop, you can do so by labelling your loops and specifying a parent loop in a break statement:

LoopA: for (let i = 0; i < 10; i++) {
    LoopB: for (let j = 0; j < 10; j++) {
        if (j === 5) {
            // Break out of child AND parent loop:
            break LoopA;
        }
    }
}

In the above example, the parent loop is labelled LoopA and the child loop is labelled LoopB.

When j is 5 in the nested loop, both LoopA and LoopB are broken.

Conclusion

That’s it! Happy loop-breaking!