JavaScript on attachevent and addeventlistener differences and compatibility notation

In Mozilla:

How to use AddEventListener:

Target.addeventlistener (type, listener, usecapture);

Target: Documentation node, document, window, or XMLHttpRequest.
Type: String, event name, without "on", such as "click", "MouseOver", "KeyDown" and so on.
Listener: Implements a EventListener interface or a function in JavaScript.
Usecapture: Whether to use snapping, generally with false. For example: document.getElementById ("Testtext"). AddEventListener ("KeyDown", function (event) {alert (event.keycode);}, False );

In IE:

Target.attachevent (type, listener);
Target: Documentation node, document, window, or XMLHttpRequest.
Type: String, event name, including "on", such as "onclick", "onmouseover", "onkeydown" and so on.
Listener: Implements a EventListener interface or a function in JavaScript. For example: document.getElementById ("TXT"). attachevent ("onclick", function (event) {alert (event.keycode);});

Compatible wording:

     if (window.attachevent) {         obj.attachevent (function() {alert (even.innerhtml)});   ie    }    else  {    obj.addeventlistener (function  false// Firefox    }

JavaScript on attachevent and addeventlistener differences and compatibility notation