jquery.ready可以在文档加载后尽快执行对文档的操作

 1 jQuery.ready.promise = function( obj ) { 2 ????if ( !readyList ) { 3 ?4 ????????readyList = jQuery.Deferred(); 5 ?6 ????????// Catch cases where $(document).ready() is called 7 ????????// after the browser event has already occurred. 8 ????????// Support: IE6-10 9 ????????// Older IE sometimes signals "interactive" too soon10 ????????if ( document.readyState === "complete" ||11 ????????????( document.readyState !== "loading" && !document.documentElement.doScroll ) ) {12 13 ????????????// Handle it asynchronously to allow scripts the opportunity to delay ready14 ????????????window.setTimeout( jQuery.ready );15 16 ????????// Standards-based browsers support DOMContentLoaded17 ????????} else if ( document.addEventListener ) {18 19 ????????????// Use the handy event callback20 ????????????document.addEventListener( "DOMContentLoaded", completed );21 22 ????????????// A fallback to window.onload, that will always work23 ????????????window.addEventListener( "load", completed );24 25 ????????// If IE event model is used26 ????????} else {27 28 ????????????// Ensure firing before onload, maybe late but safe also for iframes29 ????????????document.attachEvent( "onreadystatechange", completed );30 31 ????????????// A fallback to window.onload, that will always work32 ????????????window.attachEvent( "onload", completed );33 34 ????????????// If IE and not a frame35 ????????????// continually check to see if the document is ready36 ????????????var top = false;37 38 ????????????try {39 ????????????????top = window.frameElement == null && document.documentElement;40 ????????????} catch ( e ) {}41 42 ????????????if ( top && top.doScroll ) {43 ????????????????( function doScrollCheck() {44 ????????????????????if ( !jQuery.isReady ) {45 46 ????????????????????????try {47 48 ????????????????????????????// Use the trick by Diego Perini49 ????????????????????????????// http://javascript.nwbox.com/IEContentLoaded/50 ????????????????????????????top.doScroll( "left" );51 ????????????????????????} catch ( e ) {52 ????????????????????????????return window.setTimeout( doScrollCheck, 50 );53 ????????????????????????}54 55 ????????????????????????// detach all dom ready events56 ????????????????????????detach();57 58 ????????????????????????// and execute any waiting functions59 ????????????????????????jQuery.ready();60 ????????????????????}61 ????????????????} )();62 ????????????}63 ????????}64 ????}65 ????return readyList.promise( obj );66 };