Pass Unchangable variable to setTimeout in JavaScript

Question

First off: I am not using global variables. I'm just using them in this example to make things easier. I am actually attaching them to another object and not the window.

Here's what I'm trying to do:

window.i = 0;

while(window.i < 10){
setTimeout(function(){alert(window.i);}, 2000);

window.i++;
}

After two seconds I get ten alerts but they all say '10'. Is there a way to "convert" the variable into a unique variable in the timeout? So I can get alerts like 1, 2, 3, 4...

I can't use a string, it has to be a function. So nothing like this:

setTimeout('alert(i);', 2000);

Thanks!

gen_Eric · Accepted Answer · 2014-02-13 20:20:18Z

1

You need to make a closure to "capture" each value of i. Otherwise, each timeout will be referencing the "final" value.

var i = 0;
var timeoutFunc = function(i){
    return function(){
        alert(i);
    };
};

while(i < 10){
    setTimeout(timeoutFunc(i), 2000);

    i++;
}

answered Feb 13, 2014 at 20:20

gen_Eric

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