Jquery实现ready()的源码

 1 function bindReady(){
 2     if ( readyBound ) return;
 3     readyBound = true;
 4
 5     // Mozilla, Opera and webkit nightlies currently support this event
 6     if ( document.addEventListener ) {
 7         // Use the handy event callback
 8         document.addEventListener( "DOMContentLoaded", function(){
 9             document.removeEventListener( "DOMContentLoaded", arguments.callee, false );
10             jQuery.ready();
11         }, false );
12
13     // If IE event model is used
14     } else if ( document.attachEvent ) {
15         // ensure firing before onload,
16         // maybe late but safe also for iframes
17         document.attachEvent("onreadystatechange", function(){
18             if ( document.readyState === "complete" ) {
19                 document.detachEvent( "onreadystatechange", arguments.callee );
20                 jQuery.ready();
21             }
22         });
23
24         // If IE and not an iframe
25         // continually check to see if the document is ready
26         if ( document.documentElement.doScroll && typeof window.frameElement === "undefined" )
27           (function(){
28             if ( jQuery.isReady ) return;
29
30             try {
31                 // If IE is used, use the trick by Diego Perini
32                 // http://javascript.nwbox.com/IEContentLoaded/
33                 document.documentElement.doScroll("left");
34             } catch( error ) {
35                 setTimeout( arguments.callee, 0 );
36                 return;
37             }
38
39             // and execute any waiting functions
40             jQuery.ready();
41         })();
42     }
43
44     // A fallback to window.onload, that will always work
45     jQuery.event.add( window, "load", jQuery.ready );
46 }   

关键：IE or Webkit|Moz 内核判断、DOMContentLoaded事件、onreadystatechange事件、readyState==“complete”

Jquery实现ready()的源码