How to generate event handlers with loop in Javascript? [duplicate]

Answer 1

All of your handlers are sharing the same i variable.

You need to put each handler into a separate function that takes i as a parameter so that each one gets its own variable:

function handleElement(i) {
    document.getElementById("b"+i).onclick=function() {
        alert(i);
    };
}

for(i=1; i<11; i++) 
    handleElement(i);

Answer 2

A closure is what you're looking for:

for(i=1; i<11; i++) {
    (function(i) {
        document.getElementById("b"+i).onclick=function() {
            alert(i);
        };
    })(i);
}

Answer 3

There are two ways to use closure on this problem. The idea is to create a scope with a snapshot of "i" variable for each iteration to be used by event handler.

Solution #1 (as was mentioned by Kevin):

for(i=1; i<11; i++) {
    (function(num) {

       document.getElementById("b"+num).addEventListener('click', function() {
            alert(num);
       });

    })(i);
}

Solution #2:

for (i=1; i<11; i++) {
    document.getElementById("b"+i).addEventListener('click', (function(){
        var num = i;
        return function() {
            alert(num);
        }
    })());
}