javascript callbacks in for loop

Question

I have a for loop in a function in the structure

func(var, callback) {
    for(i = 0; i < len; i++) {
        validate(var, function(value) {
            if (!value) { callback(value) }
        }
    }
callback(true);
}

Where the function validate returns a boolean. I would only like to call my callback with true if it has not been called before. I tried putting a return after callback(value) but that didn't help.

That is correct for this example block of code. In my actual code I have meaningful variable names and my loop control is not a global variable. I just chose to use that name and not worry about the scope of i because it wasn't relevant to the question I was asking. — somethingShiny
– somethingShiny, Commented Oct 29, 2014 at 19:10

Felix Kling · Accepted Answer · 2014-10-28 18:20:52Z

1

Set a flag:

function func(foo, callback) {
    var called = false;
    for(var i = 0; i < len; i++) {
        validate(foo, function(value) {
            if (!value) {
                called = true;
                callback(value);
            }
        })
    }
    if (!called) {
        callback(true);
    }
}

answered Oct 28, 2014 at 18:20

Felix Kling

820k181 gold badges1.1k silver badges1.2k bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

somethingShiny Over a year ago

That's the only thought I had as well. I've done that and it is working. I'm not really sure why but the idea of setting a flag variable doesn't feel very clean to me. I guess it's because I'm fairly new to using callbacks and it feels like using a flag to avoid calling it multiple times seems like a very manual way of handling it, where I'm used to returning values so I haven't had to deal with this issue before.

Collectives™ on Stack Overflow

javascript callbacks in for loop

1 Answer 1

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related