Closure in Javascript [duplicate]

Answer 1

Create a closure via a self-executing function literal (or a named factory function)

function doTask(x) { alert(x); }

for(var i = 100; i--;) {
    document.getElementById('divNum' + i).onclick = (function(i) {
        return function() { doTask(i); };
    })(i);
}

or use the DOM node for information storage

function doTask() { alert(this.x); }

for(var i = 100; i--;) {
    var node = document.getElementById('divNum' + i);
    node.x = i;
    node.onclick = doTask;
}

The latter is more memory-friendly as no superfluous function objects are created.

Answer 2

Although the (correct) answer is the duplicate, I'd like to point out a more advanced method - replacing loops with iterators, which effectively solves javascript "late-bound" closures problem.

loop = function(start, end, step, body) {
    for(var i = start; i != end; i += step)
       body(i)
}

loop(1, 100, 1, function(i) {
   // your binding stuff
})