What does continue do inside a nested for loop?

Question

I have the following code:

for (var i in players) {
    for (var x in players[i].bullets) {
        for (var y in xpBoosts) {
            if (something === true) {
                // do something
                continue;
            }
        }
    }
}

What will the continue statement do? Will it cycle the innermost for loop or the outermost?

Is there any way I can get the continue statement to cycle through to the next bullet?

maybe a [dupe](/questions/11728757/why-are-continue-statements-bad-in-javascript)? — Nina Scholz, Nov 06 '18 at 21:25
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/continue — ksav, Nov 06 '18 at 21:25

score 6 · Accepted Answer · answered Nov 06 '18 at 21:27

6

continue terminates the current iteration of the loop it's in. To terminate the iteration of another loop, use it with labels:

for (var i in players) {
    bullets: for (var x in players[i].bullets) {
        for (var y in xpBoosts) {
            if (something === true) {
                // do something
                continue bullets;
            }
        }
    }
}

answered Nov 06 '18 at 21:27

OhleC

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1

I have somehow never seen this before. Ya learn something new every day. Awesome! – Tyler Roper Nov 06 '18 at 21:28
1

Good answer, I was going to update mine with the `labeled continue` but I see you've already covered it! – zfrisch Nov 06 '18 at 21:33

score 1 · Answer 2 · answered Nov 06 '18 at 21:25

In your particular code continue doesn't do anything.

continue is a keyword that will quit the current iteration of the loop and carry on with the next.

as an example:

for (i = 1; i <= 10; i++) {
  if (i == 5) continue;
  console.log(i);
}

You'll notice that 5 is not printed to the console. When the conditional check is proven true, it continues onto the next iteration without performing the rest of the code in the block.

score 1 · Answer 3 · answered Nov 06 '18 at 21:29

By default, continue and break apply to the innermost loop. In your particular code, it will continue this loop:

for (var y in xpBoosts) {

However, this behavior can be customized through labels. For example:

outerLoop:
for (var i = 0; i < someVal; i++){
  middleLoop:
  for (var j = 0; j < someOtherVal; j++){
    innerLoop:
    for (var k = 0; k < yetAThirdVal; k++){
      continue;//skip to next iteration of innerLoop
      continue innerLoop;//skip to next iteration of innerLoop
      continue middleLoop;//skip to next iteration of middleLoop
      continue outerLoop;//skip to next iteration of outerLoop
    }
  }
}

Hope this helps!

score 0 · Answer 4 · answered Nov 06 '18 at 21:26

EDIT: I'll leave my answer here, but I much prefer ohlec's answer.

continue only moves on to the next iteration of the innermost for loop.

You could have a variable that is initialized as false for each bullet. You can then mark this to true if you continue the inside loop.

for (var x in players[i].bullets) {
  var skipThisBullet = false;

  for (var y in xpBoosts) {
    if (something === true) {
      // do something
      skipThisBullet = true;
      continue;
    }
  }

  if (skipThisBullet) continue;

}

What does continue do inside a nested for loop?

4 Answers4