jquery的ready事件的实现机制浅析

jQuery.ready.promise &＃61; function( obj ) {if ( !readyList ) {readyList &＃61; jQuery.Deferred();// Catch cases where $(document).ready() is called after the browser event has already occurred.// we once tried to use readyState "interactive" here, but it caused issues like the one// discovered by ChrisS here: http://bugs.jquery.com/ticket/12282#comment:15if ( document.readyState &＃61;&＃61;&＃61; "complete" ) {// Handle it asynchronously to allow scripts the opportunity to delay readysetTimeout( jQuery.ready );// Standards-based browsers support DOMContentLoaded} else if ( document.addEventListener ) {// Use the handy event callbackdocument.addEventListener( "DOMContentLoaded", completed, false );// A fallback to window.onload, that will always workwindow.addEventListener( "load", completed, false );// If IE event model is used} else {// Ensure firing before onload, maybe late but safe also for iframesdocument.attachEvent( "onreadystatechange", completed );// A fallback to window.onload, that will always workwindow.attachEvent( "onload", completed );// If IE and not a frame// continually check to see if the document is readyvar top &＃61; false;try {top &＃61; window.frameElement &＃61;&＃61; null && document.documentElement;} catch(e) {}if ( top && top.doScroll ) {(function doScrollCheck() {if ( !jQuery.isReady ) {try {// Use the trick by Diego Perini// http://Javascript.nwbox.com/IEContentLoaded/top.doScroll("left");} catch(e) {return setTimeout( doScrollCheck, 50 );}// detach all dom ready eventsdetach();// and execute any waiting functions
jQuery.ready();}})();}}}return readyList.promise( obj );
};

document.addEventListener( "DOMContentLoaded", completed, false );

(function doScrollCheck() {if ( !jQuery.isReady ) {try {// Use the trick by Diego Perini// http://Javascript.nwbox.com/IEContentLoaded/top.doScroll("left");} catch(e) {return setTimeout( doScrollCheck, 50 );}// detach all dom ready eventsdetach();// and execute any waiting functions
jQuery.ready();}})();