src/event.js

   1 /*
   2  * A number of helper functions used for managing events.
   3  * Many of the ideas behind this code originated from
   4  * Dean Edwards' addEvent library.
   5  */
   6 jQuery.event = {
   7
   8         // Bind an event to an element
   9         // Original by Dean Edwards
  10         add: function(elem, types, handler, data) {
  11                 if ( elem.nodeType == 3 || elem.nodeType == 8 )
  12                         return;
  13
  14                 // For whatever reason, IE has trouble passing the window object
  15                 // around, causing it to be cloned in the process
  16                 if ( elem.setInterval && elem != window )
  17                         elem = window;
  18
  19                 // Make sure that the function being executed has a unique ID
  20                 if ( !handler.guid )
  21                         handler.guid = this.guid++;
  22
  23                 // if data is passed, bind to handler
  24                 if ( data !== undefined ) {
  25                         // Create temporary function pointer to original handler
  26                         var fn = handler;
  27
  28                         // Create unique handler function, wrapped around original handler
  29                         handler = this.proxy( fn, function() {
  30                                 // Pass arguments and context to original handler
  31                                 return fn.apply(this, arguments);
  32                         });
  33
  34                         // Store data in unique handler
  35                         handler.data = data;
  36                 }
  37
  38                 // Init the element's event structure
  39                 var events = jQuery.data(elem, "events") || jQuery.data(elem, "events", {}),
  40                         handle = jQuery.data(elem, "handle") || jQuery.data(elem, "handle", function(){
  41                                 // Handle the second event of a trigger and when
  42                                 // an event is called after a page has unloaded
  43                                 return typeof jQuery !== "undefined" && !jQuery.event.triggered ?
  44                                         jQuery.event.handle.apply(arguments.callee.elem, arguments) :
  45                                         undefined;
  46                         });
  47                 // Add elem as a property of the handle function
  48                 // This is to prevent a memory leak with non-native
  49                 // event in IE.
  50                 handle.elem = elem;
  51
  52                 // Handle multiple events separated by a space
  53                 // jQuery(...).bind("mouseover mouseout", fn);
  54                 jQuery.each(types.split(/\s+/), function(index, type) {
  55                         // Namespaced event handlers
  56                         var namespaces = type.split(".");
  57                         type = namespaces.shift();
  58                         handler.type = namespaces.slice().sort().join(".");
  59
  60                         // Get the current list of functions bound to this event
  61                         var handlers = events[type];
  62
  63                         if ( jQuery.event.specialAll[type] )
  64                                 jQuery.event.specialAll[type].setup.call(elem, data, namespaces);
  65
  66                         // Init the event handler queue
  67                         if (!handlers) {
  68                                 handlers = events[type] = {};
  69
  70                                 // Check for a special event handler
  71                                 // Only use addEventListener/attachEvent if the special
  72                                 // events handler returns false
  73                                 if ( !jQuery.event.special[type] || jQuery.event.special[type].setup.call(elem, data, namespaces) === false ) {
  74                                         // Bind the global event handler to the element
  75                                         if (elem.addEventListener)
  76                                                 elem.addEventListener(type, handle, false);
  77                                         else if (elem.attachEvent)
  78                                                 elem.attachEvent("on" + type, handle);
  79                                 }
  80                         }
  81
  82                         // Add the function to the element's handler list
  83                         handlers[handler.guid] = handler;
  84
  85                         // Keep track of which events have been used, for global triggering
  86                         jQuery.event.global[type] = true;
  87                 });
  88
  89                 // Nullify elem to prevent memory leaks in IE
  90                 elem = null;
  91         },
  92
  93         guid: 1,
  94         global: {},
  95
  96         // Detach an event or set of events from an element
  97         remove: function(elem, types, handler) {
  98                 // don't do events on text and comment nodes
  99                 if ( elem.nodeType == 3 || elem.nodeType == 8 )
 100                         return;
 101
 102                 var events = jQuery.data(elem, "events"), ret, index;
 103
 104                 if ( events ) {
 105                         // Unbind all events for the element
 106                         if ( types === undefined || (typeof types === "string" && types.charAt(0) == ".") )
 107                                 for ( var type in events )
 108                                         this.remove( elem, type + (types || "") );
 109                         else {
 110                                 // types is actually an event object here
 111                                 if ( types.type ) {
 112                                         handler = types.handler;
 113                                         types = types.type;
 114                                 }
 115
 116                                 // Handle multiple events seperated by a space
 117                                 // jQuery(...).unbind("mouseover mouseout", fn);
 118                                 jQuery.each(types.split(/\s+/), function(index, type){
 119                                         // Namespaced event handlers
 120                                         var namespaces = type.split(".");
 121                                         type = namespaces.shift();
 122                                         var namespace = RegExp("(^|\\.)" + namespaces.slice().sort().join(".*\\.") + "(\\.|$)");
 123
 124                                         if ( events[type] ) {
 125                                                 // remove the given handler for the given type
 126                                                 if ( handler )
 127                                                         delete events[type][handler.guid];
 128
 129                                                 // remove all handlers for the given type
 130                                                 else
 131                                                         for ( handler in events[type] )
 132                                                                 // Handle the removal of namespaced events
 133                                                                 if ( namespace.test(events[type][handler].type) )
 134                                                                         delete events[type][handler];
 135
 136                                                 if ( jQuery.event.specialAll[type] )
 137                                                         jQuery.event.specialAll[type].teardown.call(elem, namespaces);
 138
 139                                                 // remove generic event handler if no more handlers exist
 140                                                 for ( ret in events[type] ) break;
 141                                                 if ( !ret ) {
 142                                                         if ( !jQuery.event.special[type] || jQuery.event.special[type].teardown.call(elem, namespaces) === false ) {
 143                                                                 if (elem.removeEventListener)
 144                                                                         elem.removeEventListener(type, jQuery.data(elem, "handle"), false);
 145                                                                 else if (elem.detachEvent)
 146                                                                         elem.detachEvent("on" + type, jQuery.data(elem, "handle"));
 147                                                         }
 148                                                         ret = null;
 149                                                         delete events[type];
 150                                                 }
 151                                         }
 152                                 });
 153                         }
 154
 155                         // Remove the expando if it's no longer used
 156                         for ( ret in events ) break;
 157                         if ( !ret ) {
 158                                 var handle = jQuery.data( elem, "handle" );
 159                                 if ( handle ) handle.elem = null;
 160                                 jQuery.removeData( elem, "events" );
 161                                 jQuery.removeData( elem, "handle" );
 162                         }
 163                 }
 164         },
 165
 166         trigger: function( event, data, elem, extra) {
 167                 // Event object or event type
 168                 var type = event.type || event;
 169
 170                 event = typeof event === "object" ?
 171                         // jQuery.Event object
 172                         event[expando] ? event :
 173                         // Object literal
 174                         jQuery.extend( jQuery.Event(type), event ) :
 175                         // Just the event type (string)
 176                         jQuery.Event(type);
 177
 178                 if ( type.indexOf("!") >= 0 ) {
 179                         event.type = type = type.slice(0, -1);
 180                         event.exclusive = true;
 181                 }
 182
 183                 // Handle a global trigger
 184                 if ( !elem ) {
 185                         // Don't bubble custom events when global (to avoid too much overhead)
 186                         event.stopPropagation();
 187                         // Only trigger if we've ever bound an event for it
 188                         if ( this.global[type] )
 189                                 jQuery.each( jQuery.cache, function(){
 190                                         if ( this.events && this.events[type] )
 191                                                 jQuery.event.trigger( event, data, this.handle.elem );
 192                                 });
 193
 194                 // Handle triggering a single element
 195                 } else {
 196
 197                         // don't do events on text and comment nodes
 198                         if ( elem.nodeType == 3 || elem.nodeType == 8 )
 199                                 return undefined;
 200
 201                         // Clone the incoming data, if any
 202                         data = jQuery.makeArray(data);
 203
 204                         // AT_TARGET phase (not bubbling)
 205                         if( !event.target ){
 206                                 // Clean up in case it is reused
 207                                 event.result = undefined;
 208                                 event.target = elem;
 209                         }
 210
 211                         // Fix for custom events
 212                         event.currentTarget = elem;
 213
 214                         data.unshift( event );
 215
 216                         var fn = jQuery.isFunction( elem[ type ] );
 217
 218                         // Trigger the event, it is assumed that "handle" is a function
 219                         var handle = jQuery.data(elem, "handle");
 220                         if ( handle )
 221                                 handle.apply( elem, data );
 222
 223                         // Handle triggering native .onfoo handlers (and on links since we don't call .click() for links)
 224                         if ( (!fn || (jQuery.nodeName(elem, 'a') && type == "click")) && elem["on"+type] && elem["on"+type].apply( elem, data ) === false )
 225                                 event.result = false;
 226
 227                         // Extra functions don't get the custom event object
 228                         data.shift();
 229
 230                         // Handle triggering of extra function
 231                         if ( extra && jQuery.isFunction( extra ) ) {
 232                                 // call the extra function and tack the current return value on the end for possible inspection
 233                                 var ret = extra.apply( elem, event.result == null ? data : data.concat( event.result ) );
 234                                 // if anything is returned, give it precedence and have it overwrite the previous value
 235                                 if ( ret !== undefined )
 236                                         event.result = ret;
 237                         }
 238
 239                         // Trigger the native events (except for clicks on links)
 240                         if ( event.target === elem && fn && !event.isDefaultPrevented() && !(jQuery.nodeName(elem, 'a') && type == "click") ) {
 241                                 this.triggered = true;
 242                                 try {
 243                                         elem[ type ]();
 244                                 // prevent IE from throwing an error for some hidden elements
 245                                 } catch (e) {}
 246                         }
 247
 248                         if ( !event.isPropagationStopped() ) {
 249                                 var parent = elem.parentNode || elem.ownerDocument;
 250                                 if ( parent )
 251                                         jQuery.event.trigger(event, data, parent);
 252                         }
 253
 254                         // Clean up, in case the event object is reused
 255                         event.target = null;
 256
 257                         this.triggered = false;
 258                 }
 259         },
 260
 261         handle: function(event) {
 262                 // returned undefined or false
 263                 var all, handlers;
 264
 265                 event = arguments[0] = jQuery.event.fix( event || window.event );
 266
 267                 // Namespaced event handlers
 268                 var namespaces = event.type.split(".");
 269                 event.type = namespaces.shift();
 270
 271                 // Cache this now, all = true means, any handler
 272                 all = !namespaces.length && !event.exclusive;
 273
 274                 var namespace = RegExp("(^|\\.)" + namespaces.slice().sort().join(".*\\.") + "(\\.|$)");
 275
 276                 handlers = ( jQuery.data(this, "events") || {} )[event.type];
 277
 278                 for ( var j in handlers ) {
 279                         var handler = handlers[j];
 280
 281                         // Filter the functions by class
 282                         if ( all || namespace.test(handler.type) ) {
 283                                 // Pass in a reference to the handler function itself
 284                                 // So that we can later remove it
 285                                 event.handler = handler;
 286                                 event.data = handler.data;
 287
 288                                 var ret = handler.apply(this, arguments);
 289
 290                                 if( ret !== undefined ){
 291                                         event.result = ret;
 292                                         if ( ret === false ) {
 293                                                 event.preventDefault();
 294                                                 event.stopPropagation();
 295                                         }
 296                                 }
 297
 298                                 if( event.isImmediatePropagationStopped() )
 299                                         break;
 300
 301                         }
 302                 }
 303         },
 304
 305         props: "altKey attrChange attrName bubbles button cancelable charCode clientX clientY ctrlKey currentTarget data detail eventPhase fromElement handler keyCode metaKey newValue originalTarget pageX pageY prevValue relatedNode relatedTarget screenX screenY shiftKey srcElement target toElement view wheelDelta which".split(" "),
 306
 307         fix: function(event) {
 308                 if ( event[expando] )
 309                         return event;
 310
 311                 // store a copy of the original event object
 312                 // and "clone" to set read-only properties
 313                 var originalEvent = event;
 314                 event = jQuery.Event( originalEvent );
 315
 316                 for ( var i = this.props.length, prop; i; ){
 317                         prop = this.props[ --i ];
 318                         event[ prop ] = originalEvent[ prop ];
 319                 }
 320
 321                 // Fix target property, if necessary
 322                 if ( !event.target )
 323                         event.target = event.srcElement || document; // Fixes #1925 where srcElement might not be defined either
 324
 325                 // check if target is a textnode (safari)
 326                 if ( event.target.nodeType == 3 )
 327                         event.target = event.target.parentNode;
 328
 329                 // Add relatedTarget, if necessary
 330                 if ( !event.relatedTarget && event.fromElement )
 331                         event.relatedTarget = event.fromElement == event.target ? event.toElement : event.fromElement;
 332
 333                 // Calculate pageX/Y if missing and clientX/Y available
 334                 if ( event.pageX == null && event.clientX != null ) {
 335                         var doc = document.documentElement, body = document.body;
 336                         event.pageX = event.clientX + (doc && doc.scrollLeft || body && body.scrollLeft || 0) - (doc.clientLeft || 0);
 337                         event.pageY = event.clientY + (doc && doc.scrollTop || body && body.scrollTop || 0) - (doc.clientTop || 0);
 338                 }
 339
 340                 // Add which for key events
 341                 if ( !event.which && ((event.charCode || event.charCode === 0) ? event.charCode : event.keyCode) )
 342                         event.which = event.charCode || event.keyCode;
 343
 344                 // Add metaKey to non-Mac browsers (use ctrl for PC's and Meta for Macs)
 345                 if ( !event.metaKey && event.ctrlKey )
 346                         event.metaKey = event.ctrlKey;
 347
 348                 // Add which for click: 1 == left; 2 == middle; 3 == right
 349                 // Note: button is not normalized, so don't use it
 350                 if ( !event.which && event.button )
 351                         event.which = (event.button & 1 ? 1 : ( event.button & 2 ? 3 : ( event.button & 4 ? 2 : 0 ) ));
 352
 353                 return event;
 354         },
 355
 356         proxy: function( fn, proxy ){
 357                 // Set the guid of unique handler to the same of original handler, so it can be removed
 358                 proxy.guid = fn.guid = fn.guid || proxy.guid || this.guid++;
 359                 // So proxy can be declared as an argument
 360                 return proxy;
 361         },
 362
 363         special: {
 364                 ready: {
 365                         // Make sure the ready event is setup
 366                         setup: bindReady,
 367                         teardown: function() {}
 368                 }
 369         },
 370
 371         specialAll: {
 372                 live: {
 373                         setup: function( selector, namespaces ){
 374                                 jQuery.event.add( this, namespaces[0], liveHandler );
 375                         },
 376                         teardown:  function( namespaces ){
 377                                 if ( namespaces.length ) {
 378                                         var remove = 0, name = RegExp("(^|\\.)" + namespaces[0] + "(\\.|$)");
 379
 380                                         jQuery.each( (jQuery.data(this, "events").live || {}), function(){
 381                                                 if ( name.test(this.type) )
 382                                                         remove++;
 383                                         });
 384
 385                                         if ( remove <= 1 )
 386                                                 jQuery.event.remove( this, namespaces[0], liveHandler );
 387                                 }
 388                         }
 389                 }
 390         }
 391 };
 392
 393 jQuery.Event = function( src ){
 394         // Allow instantiation without the 'new' keyword
 395         if( !this.preventDefault )
 396                 return new jQuery.Event(src);
 397
 398         // Event object
 399         if( src && src.type ){
 400                 this.originalEvent = src;
 401                 this.type = src.type;
 402
 403                 // Fix timeStamp
 404                 this.timeStamp = src.timeStamp || now();
 405         // Event type
 406         }else
 407                 this.type = src;
 408
 409         // Mark it as fixed
 410         this[expando] = true;
 411 };
 412
 413 function returnFalse(){
 414         return false;
 415 }
 416 function returnTrue(){
 417         return true;
 418 }
 419
 420 // jQuery.Event is based on DOM3 Events as specified by the ECMAScript Language Binding
 421 // http://www.w3.org/TR/2003/WD-DOM-Level-3-Events-20030331/ecma-script-binding.html
 422 jQuery.Event.prototype = {
 423         preventDefault: function() {
 424                 this.isDefaultPrevented = returnTrue;
 425
 426                 var e = this.originalEvent;
 427                 if( !e )
 428                         return;
 429                 // if preventDefault exists run it on the original event
 430                 if (e.preventDefault)
 431                         e.preventDefault();
 432                 // otherwise set the returnValue property of the original event to false (IE)
 433                 e.returnValue = false;
 434         },
 435         stopPropagation: function() {
 436                 this.isPropagationStopped = returnTrue;
 437
 438                 var e = this.originalEvent;
 439                 if( !e )
 440                         return;
 441                 // if stopPropagation exists run it on the original event
 442                 if (e.stopPropagation)
 443                         e.stopPropagation();
 444                 // otherwise set the cancelBubble property of the original event to true (IE)
 445                 e.cancelBubble = true;
 446         },
 447         stopImmediatePropagation:function(){
 448                 this.isImmediatePropagationStopped = returnTrue;
 449                 this.stopPropagation();
 450         },
 451         isDefaultPrevented: returnFalse,
 452         isPropagationStopped: returnFalse,
 453         isImmediatePropagationStopped: returnFalse
 454 };
 455 // Checks if an event happened on an element within another element
 456 // Used in jQuery.event.special.mouseenter and mouseleave handlers
 457 var withinElement = function(event) {
 458         // Check if mouse(over|out) are still within the same parent element
 459         var parent = event.relatedTarget;
 460         // Traverse up the tree
 461         while ( parent && parent != this )
 462                 try { parent = parent.parentNode; }
 463                 catch(e) { parent = this; }
 464
 465         if( parent != this ){
 466                 // set the correct event type
 467                 event.type = event.data;
 468                 // handle event if we actually just moused on to a non sub-element
 469                 jQuery.event.handle.apply( this, arguments );
 470         }
 471 };
 472
 473 jQuery.each({
 474         mouseover: 'mouseenter',
 475         mouseout: 'mouseleave'
 476 }, function( orig, fix ){
 477         jQuery.event.special[ fix ] = {
 478                 setup: function(){
 479                         jQuery.event.add( this, orig, withinElement, fix );
 480                 },
 481                 teardown: function(){
 482                         jQuery.event.remove( this, orig, withinElement );
 483                 }
 484         };
 485 });
 486
 487 jQuery.fn.extend({
 488         bind: function( type, data, fn ) {
 489                 return type == "unload" ? this.one(type, data, fn) : this.each(function(){
 490                         jQuery.event.add( this, type, fn || data, fn && data );
 491                 });
 492         },
 493
 494         one: function( type, data, fn ) {
 495                 var one = jQuery.event.proxy( fn || data, function(event) {
 496                         jQuery(this).unbind(event, one);
 497                         return (fn || data).apply( this, arguments );
 498                 });
 499                 return this.each(function(){
 500                         jQuery.event.add( this, type, one, fn && data);
 501                 });
 502         },
 503
 504         unbind: function( type, fn ) {
 505                 return this.each(function(){
 506                         jQuery.event.remove( this, type, fn );
 507                 });
 508         },
 509
 510         trigger: function( type, data, fn ) {
 511                 return this.each(function(){
 512                         jQuery.event.trigger( type, data, this, fn );
 513                 });
 514         },
 515
 516         triggerHandler: function( type, data, fn ) {
 517                 if( this[0] ){
 518                         var event = jQuery.Event(type);
 519                         event.preventDefault();
 520                         event.stopPropagation();
 521                         jQuery.event.trigger( event, data, this[0], fn );
 522                         return event.result;
 523                 }
 524         },
 525
 526         toggle: function( fn ) {
 527                 // Save reference to arguments for access in closure
 528                 var args = arguments, i = 1;
 529
 530                 // link all the functions, so any of them can unbind this click handler
 531                 while( i < args.length )
 532                         jQuery.event.proxy( fn, args[i++] );
 533
 534                 return this.click( jQuery.event.proxy( fn, function(event) {
 535                         // Figure out which function to execute
 536                         this.lastToggle = ( this.lastToggle || 0 ) % i;
 537
 538                         // Make sure that clicks stop
 539                         event.preventDefault();
 540
 541                         // and execute the function
 542                         return args[ this.lastToggle++ ].apply( this, arguments ) || false;
 543                 }));
 544         },
 545
 546         hover: function(fnOver, fnOut) {
 547                 return this.mouseenter(fnOver).mouseleave(fnOut);
 548         },
 549
 550         ready: function(fn) {
 551                 // Attach the listeners
 552                 bindReady();
 553
 554                 // If the DOM is already ready
 555                 if ( jQuery.isReady )
 556                         // Execute the function immediately
 557                         fn.call( document, jQuery );
 558
 559                 // Otherwise, remember the function for later
 560                 else
 561                         // Add the function to the wait list
 562                         jQuery.readyList.push( function() { return fn.call(this, jQuery); } );
 563
 564                 return this;
 565         },
 566
 567         live: function( type, fn ){
 568                 jQuery(document).bind( liveConvert(type, this.selector), this.selector, fn );
 569                 return this;
 570         },
 571
 572         die: function( type, fn ){
 573                 jQuery(document).unbind( liveConvert(type, this.selector), fn );
 574                 return this;
 575         }
 576 });
 577
 578 function liveHandler( event ){
 579         var check = RegExp("(^|\\.)" + event.type + "(\\.|$)"),
 580                 stop = true;
 581
 582         jQuery.each(jQuery.data(this, "events").live || [], function(i, fn){
 583                 if ( check.test(fn.type) ) {
 584                         var elem = jQuery(event.target).closest(fn.data)[0];
 585                         if ( elem && fn.call(elem, event, fn.data) === false )
 586                                 stop = false;
 587                 }
 588         });
 589         return stop;
 590 }
 591
 592 function liveConvert(type, selector){
 593         return ["live", type, selector.replace(/\./g, "_")].join(".");
 594 }
 595
 596 jQuery.extend({
 597         isReady: false,
 598         readyList: [],
 599         // Handle when the DOM is ready
 600         ready: function() {
 601                 // Make sure that the DOM is not already loaded
 602                 if ( !jQuery.isReady ) {
 603                         // Remember that the DOM is ready
 604                         jQuery.isReady = true;
 605
 606                         // If there are functions bound, to execute
 607                         if ( jQuery.readyList ) {
 608                                 // Execute all of them
 609                                 jQuery.each( jQuery.readyList, function(){
 610                                         this.call( document );
 611                                 });
 612
 613                                 // Reset the list of functions
 614                                 jQuery.readyList = null;
 615                         }
 616
 617                         // Trigger any bound ready events
 618                         jQuery(document).triggerHandler("ready");
 619                 }
 620         }
 621 });
 622
 623 var readyBound = false;
 624
 625 function bindReady(){
 626         if ( readyBound ) return;
 627         readyBound = true;
 628
 629         // Mozilla, Opera and webkit nightlies currently support this event
 630         if ( document.addEventListener ) {
 631                 // Use the handy event callback
 632                 document.addEventListener( "DOMContentLoaded", function(){
 633                         document.removeEventListener( "DOMContentLoaded", arguments.callee, false );
 634                         jQuery.ready();
 635                 }, false );
 636
 637         // If IE event model is used
 638         } else if ( document.attachEvent ) {
 639                 // ensure firing before onload,
 640                 // maybe late but safe also for iframes
 641                 document.attachEvent("onreadystatechange", function(){
 642                         if ( document.readyState === "complete" ) {
 643                                 document.detachEvent( "onreadystatechange", arguments.callee );
 644                                 jQuery.ready();
 645                         }
 646                 });
 647
 648                 // If IE and not an iframe
 649                 // continually check to see if the document is ready
 650                 if ( document.documentElement.doScroll && !window.frameElement ) (function(){
 651                         if ( jQuery.isReady ) return;
 652
 653                         try {
 654                                 // If IE is used, use the trick by Diego Perini
 655                                 // http://javascript.nwbox.com/IEContentLoaded/
 656                                 document.documentElement.doScroll("left");
 657                         } catch( error ) {
 658                                 setTimeout( arguments.callee, 0 );
 659                                 return;
 660                         }
 661
 662                         // and execute any waiting functions
 663                         jQuery.ready();
 664                 })();
 665         }
 666
 667         // A fallback to window.onload, that will always work
 668         jQuery.event.add( window, "load", jQuery.ready );
 669 }
 670
 671 jQuery.each( ("blur,focus,load,resize,scroll,unload,click,dblclick," +
 672         "mousedown,mouseup,mousemove,mouseover,mouseout,mouseenter,mouseleave," +
 673         "change,select,submit,keydown,keypress,keyup,error").split(","), function(i, name){
 674
 675         // Handle event binding
 676         jQuery.fn[name] = function(fn){
 677                 return fn ? this.bind(name, fn) : this.trigger(name);
 678         };
 679 });
 680
 681 // Prevent memory leaks in IE
 682 // And prevent errors on refresh with events like mouseover in other browsers
 683 // Window isn't included so as not to unbind existing unload events
 684 jQuery( window ).bind( 'unload', function(){
 685         for ( var id in jQuery.cache )
 686                 // Skip the window
 687                 if ( id != 1 && jQuery.cache[ id ].handle )
 688                         jQuery.event.remove( jQuery.cache[ id ].handle.elem );
 689 });