Adding event to an element (backward compatable)

addEventHandler.js

/**
* @param {Object} el Element where the event needed to be added
* @param {string} type Type of event which is getting added
* @param {function} handler Event handler which will get called.
*/
function addHandler(el, type, handler) { 
    //overwrite the existing function
    if (el.addEventListener){ //DOM2 Events
        addHandler = function(el, type, handler) {
            el.addEventListener(type, handler, false)
        };
    } else { //IE
        addHandler = function(el, type, handler) {
            el.attachEvent("on" + type, handler)
        };
    }
    //call the new function
    addHandler(el, type, handler);
}