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;
  }
}

Carn

Yes? Why wouldn't you be able to? – Croix

Why don't you try it yourself? Add a debugger or console log inside the conditions – Banquer

@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? – Croix

@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! – Carn

@Persijn It's not about simplicity. A user with 125+ questions asking "Debug this for me" when they can easily do it themselves – Banquer

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. – Wrongheaded

@Wrongheaded that's a fair point. – Banquer

Answer 1

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.)

Farnham

There probably is a way to get the same behavior in forEach. That could be another good question. – Wrongheaded

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), which is a difference it has with continue – Rotate

Not all blocks - just loops and switches. – Farnham

... and labelled blocks. – Stereophonic

Oh yes, those too @Teemu. – Farnham

@Wrongheaded there are already questions about break and continue in forEach... – Clarita

In forEach you can use return if a condition is not met. Though it's not very idiomatic. – Systaltic