Can I use continue and break in Javascript for...in and for...of loops?

Question

Can I use the break and continue statements inside the for...in and for...of type of loops? Or are they only accessible inside regular for loops.

Example:

myObject = { 
  propA: 'foo', 
  propB: 'bar'
};

for (let propName in myObject) {
  if (propName !== 'propA') {
    continue;
  }
  else if (propName === 'propA') {
    break;
  }
}

Why don't you try it yourself? Add a debugger or console log inside the conditions — adiga, Jul 01 '19 at 08:44
@Persijn lack of research. It's *too* simple - just running the code already present with a minor alteration (add a log statement) reveals the answer. Not to mention the *thousands* of other resources online. If the question was "can I use a different name than `propName` in my code", would you still say it's a good question? — VLAZ, Jul 01 '19 at 08:50
@Persijn Thanks. I was wondering the same thing. Two close votes on "unclear what you're asking for". How can this question not be clear? I know I could test this myself. But before testing, I searched on StackOverflow trying to find the answer. And I couldn't find one. So I asked! — cbdeveloper, Jul 01 '19 at 08:51
@Persijn It's not about simplicity. A user with 125+ questions asking "*Debug this for me*" when they can easily do it themselves — adiga, Jul 01 '19 at 08:51
I see the question as good, since I can see other users searching for this. And i can see value in having this question on stackoverflow even if its possible to find the answer other places. — Persijn, Jul 01 '19 at 08:59

Jack Bashford · Accepted Answer · 2019-07-01T08:49:54.090

41

Yep - works in all loops.

const myObject = { 
  propA: 'foo', 
  propB: 'bar'
};

for (let propName in myObject) {
  console.log(propName);
  if (propName !== 'propA') {
    continue;
  }
  else if (propName === 'propA') {
    break;
  }
}

(By loops I mean for, for...in, for...of, while and do...while, not forEach, which is actually a function defined on the Array prototype.)

edited Jul 01 '19 at 08:49

answered Jul 01 '19 at 08:44

Jack Bashford

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There probably is a way to get the same behavior in forEach. That could be another good question. – Persijn Jul 01 '19 at 08:47
1

I would argue that `forEach` is not really a loop, but a function with a callback argument. Also, `break` is not restricted to loops but to all [blocks (MDN link)](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/block), which is a difference it has with `continue` – Kaddath Jul 01 '19 at 08:49
2

Not all blocks - just loops and switches. – Jack Bashford Jul 01 '19 at 08:50
2

... and labelled blocks. – Teemu Jul 01 '19 at 08:52
Oh yes, those too @Teemu. – Jack Bashford Jul 01 '19 at 08:52
@Persijn there are already questions about `break` and `continue` in `forEach`... – barbsan Jul 01 '19 at 09:30
In `forEach` you can use `return` if a condition is not met. Though it's not very idiomatic. – Lucio Mollinedo Nov 24 '22 at 20:37

Can I use continue and break in Javascript for...in and for...of loops?

1 Answers1