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Question

How to count to 3?

Answer 1

+4 A:

for (var i = 1; i <= 3; ++i) {
    setTimeout((function (x) {
        return function () { alert(x); }
    })(i), i * 1000);
}

deceze 2010-10-28 01:57:22

Perhaps you could add some explanation as well?

rchern 2010-10-28 01:59:27

@rchern I wouldn't mind, but this has been explained a [thousand times over](http://stackoverflow.com/questions/tagged/javascript+loops+closures) already and this question seems destined for quick closure (pun intended) as duplicate of one of these. Also, the OP seems to understand the problem, he was just looking for the syntax.

deceze 2010-10-28 02:01:23

Why give half an answer then? If you know it is going to be closed? *shrugs*

rchern 2010-10-28 02:05:02

@rchern Why not? Isn't half an answer better than no answer? *shrugs* :)

deceze 2010-10-28 02:09:06

@deceze: But a full answer is still better than a half answer.

BrunoLM 2010-10-28 02:10:09

@Bruno But a full answer seemed like a waste of time, since it won't serve anybody in the future, since the question is now closed. Sorry for providing half-assed help. The weather is bad, okay? ;o)

deceze 2010-10-28 02:12:28

I don't understand answering a question you're voting to close as a dupe. Isn't it contradictory?

rchern 2010-10-28 02:29:30

@rchern Closing is a long-term clean up/maintenance thing, it doesn't mean I can't also give the OP a direct answer which helps him immediately.

deceze 2010-10-28 02:36:53

Thanks deceze :) That's correct, I didn't need an explanation of closures... I just forgot what syntax to use. I knew I could create one by creating an anonymous function and calling it immediately, but the part I was forgetting was that I needed to return a new function.

Mark 2010-10-28 02:45:10

@everybody There you go. Awesome, -2 on a correct and accepted answer. Is there a badge for that? :o)

deceze 2010-10-28 02:46:56

I think I solved this before by putting the closure around the `setTimeout` and without the return.. I was trying to put it inside the `setTimeout` this time and it wasn't working.

Mark 2010-10-28 02:47:33

Answer 2

+4 A:

That is a very common issue. With JS 1.7 this is easily solved using let keyword. To check browser version equivalency click here.

You can workaround this using closures. Create a scope for i and return the function for setTimeout.

for (var i = 1; i <= 3; ++i) {
    setTimeout((function(i) { /* i is now a parameter */
        return function () { /* this function is the one that will execute */
            alert(i); /* this `i` is not the same as the one used on the loop */
        }
    })(i), i * 1000);
}

BrunoLM 2010-10-28 02:07:06

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How to count to 3?

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