CODEWITHSUNDEEP
javascriptnode.jsbreak
meallhour
meallhour

Reputation: 15639

Break statement not exiting all nested loops within JavaScript

I am having the understanding that break statement terminates all nested loops. I have written the following code and it is not working as expected.

<script>
    for (i = 0; i < 5; i++) {
        for (j = 0; j < 5; j++) {
            if (i == 3) {
                break;
            }
            document.write(i + '*' + j + '<br>');
        }
    }
</script>

Actual Output:

0*0
0*1
0*2
0*3
0*4
1*0
1*1
1*2
1*3
1*4
2*0
2*1
2*2
2*3
2*4
4*0
4*1
4*2
4*3
4*4

As per my understanding, the output should not include 4*0...4*4 because when i == 3, the break should terminate all nested loops.

Expected Output:

0*0
0*1
0*2
0*3
0*4
1*0
1*1
1*2
1*3
1*4
2*0
2*1
2*2
2*3
2*4

Upvotes: 3

Views: 3881

Answers (4)

Paweł
Paweł

Reputation: 4536

Why don't you place a break in the first loop?

<script>
  for (i = 0; i < 5; i++) {
    if (i == 3) break;
    for (j = 0; j < 5; j++) {
      document.write(i + '*' + j + '<br>');
    }
  }
</script>

Upvotes: 1

anees
anees

Reputation: 1855

By default the only innermost loop is escaped but you can achieve the behaviour you are expecting by a self enclosing function and a return statement.

(function(){
    for (i = 0; i < 5; i++) {
        for (j = 0; j < 5; j++) {
            if (i == 3) {
                return;
            }
            document.write(i + '*' + j + '<br>');
        }
    }
})()

Upvotes: 0

Matti Greff
Matti Greff

Reputation: 238

You have to specify which loop you are breaking from.

loop1: for (i = 0; i < 5; i++) {
    loop2: for (j = 0; j < 5; j++) {
        if (i == 3) {
            break loop1;
        }
        document.write(i + '*' + j + '<br>');
    }
}

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/break

Upvotes: 10

user13124036
user13124036

Reputation:

No, break only breaks the current loop, not all of them. You can use a boolean variable to break out of the enclosing loop as well.

Example:

<script>
    let break = false
    for (i = 0; i < 5; i++) {
        for (j = 0; j < 5; j++) {
            if (i == 3) {
                break = true;
                break;
            }
            document.write(i + '*' + j + '<br>');
        }
        if(break) break
    }
</script>

Upvotes: 0

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