Javascript variables inherited by functions [duplicate]

Question

Possible Duplicate:
Javascript: closure of loop?

Pseudo javascript:

for (i, i<10, i++) {
  new element.addEvent('click', function(){ alert(i) }).inject(dom)
}

When the loop finishes all the onclick events will trigger alerts with the 'final' value of i. What is the 'correct' way of having them alert the value of i as it was when the onclick event was added?

When I say correct I mean that I'm aware there are several ways of achiving this behavior, but I want to know the standard (ie expected by people that may encounter the code) way. Thanks.

candidate for most often asked question...

Thilo
– Thilo

2012-06-19 07:43:04 +00:00
Commented Jun 19, 2012 at 7:43 — Thilo
– Thilo, Commented Jun 19, 2012 at 7:43
@FlorianMargaine There are yet 4 closing votes.

Denys Séguret
– Denys Séguret

2012-06-19 07:45:04 +00:00
Commented Jun 19, 2012 at 7:45 — Denys Séguret
– Denys Séguret, Commented Jun 19, 2012 at 7:45

James Allardice · Accepted Answer · 2012-06-19 11:26:07Z

3

Use a closure to capture the value of i at each iteration:

for (i; i<10; i++) {
    (function(i) {
         new element.addEvent('click', function(){ alert(i) }).inject(dom);
    }(i));
}

edited Jun 19, 2012 at 11:26

answered Jun 19, 2012 at 7:44

James Allardice

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9 Comments

ThiefMaster Over a year ago

Why the downvote? While it's not valid JavaScript it does answer the question in the same pseudocode-way the OP used.

Florian Margaine Over a year ago

I downvoted because he could have closed to vote instead of answering this. Avoiding SO pollution, etc.

James Allardice Over a year ago

@FlorianMargaine - Look at the list of people who closed. I am one of them. While it is a duplicate, I feel it can still be helpful to a new SO user to receive a direct answer.

Florian Margaine Over a year ago

Alright. Removed the downvote :)

Asherah Over a year ago

While we're here, we might as well use the correct for syntax. (what are those commas doing?)

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