Question

This code does not seem to be running correctly:

var addEventListener = (function () {
    "use strict";
    if (document.addEventListener) {
        return function (element, event, handler) {
            element.addEventListener(event, handler, false);
        };
    } else {
        return function (element, event, handler) {
            element.attachEvent('on' + event, handler);
        };
    }
})();

addEventListener(window, 'onload', calcFailback);

Chrome returns:

Uncaught TypeError: Object onload has no method ‘addEventListener’

Jslint returns:

Unexpected else.

Any ideas?

Answer 1

You are creating a global variable addEventListener, it will be added as a property of window. So window.addEventListener (element === window, with this call) is actually referring to your custom function, not the native one. Use different name:

var myAddEventListener = (function() {
    "use strict";
    if (document.addEventListener) {
        return function(element, event, handler) {
            element.addEventListener(event, handler, false);
        };
    } else {
        return function(element, event, handler) {
            element.attachEvent('on' + event, handler);
        };
    }
})(); //<-- invoke it

Also use "load":

myAddEventListener( window, "load", function(){})