Talk about the difference between Document.ready and window.onload

In jquery, we can see two ways of writing: $ (function () {}) and $ (document). Ready (function () {})

Both of these methods have the same effect, which is to execute a function after the DOM document tree has been loaded (note that the document tree inside does not load all of the files).

Instead, Window.onload executes a function after the DOM document tree has been loaded and all files have been loaded. That is, $ (document). Ready is executed before window.onload.

So jquery inside $ (document). How is the inside of the ready function implemented? Let's take a look at the following:

Let's add a ready function to the document:

Document.ready = function (callback) {///compatible Ff,google if (Document.addeventlistener) { Document.addeventlistener (' domcontentloaded ', function () {Document.removeeventlistener (' Domcontentl                    Oaded ', Arguments.callee, false);                Callback (); }, False)}//compatible with IE else if (document.attachevent) {document.attachevent ( ' Onreadytstatechange ', function () {if (document.readystate = = "complete") {
Document.detachevent ("onReadyStateChange", Arguments.callee);
Callback ();
}})} else if (Document.lastchild = = document.body) {callback (); }        }

Document.ready this function is implemented. Let's try to verify that the "Ready is going to be performed before OnLoad" is the top of the list:

   Window.onload = function () {            alert (' onload ');        };        Document.ready (function () {            alert (' Ready ');        });

After executing this code, you will see that the browser pops up "ready" and the onload pops up.

Talk about the difference between Document.ready and window.onload