javascript事件之：jQuery.event.dispatch详解

　　jQuery.event.dispatch，字面意思是事件分发。就是执行绑定的函数。

　　在jQuery.event.add中，

//1, jQuery.event.add中
jQuery.event.dispatch.apply( eventHandle.elem, arguments )
//2, jQuery.event.simulate中
jQuery.event.dispatch.call( elem, e );

　 我们来看看jQuery.event.dispatch的源码，看看其实现了什么。

dispatch: function( event ) {

    // 修正事件源对象
    event = jQuery.event.fix( event );
    var i, j, ret, matched, handleObj,
        handlerQueue = [],
        args = core_slice.call( arguments ),
        //得到绑定的事件对象
        handlers = ( data_priv.get( this, "events" ) || {} )[ event.type ] || [],
        special = jQuery.event.special[ event.type ] || {};
    args[0] = event;
    event.delegateTarget = this;
    // Call the preDispatch hook for the mapped type, and let it bail if desired
    if ( special.preDispatch && special.preDispatch.call( this, event ) === false ) {
        return;
    }

    // 得到handler的执行队列
    handlerQueue = jQuery.event.handlers.call( this, event, handlers );

    // Run delegates first; they may want to stop propagation beneath us
    i = 0;
    while ( (matched = handlerQueue[ i++ ]) && !event.isPropagationStopped() ) {
        event.currentTarget = matched.elem;

        j = 0;
        while ( (handleObj = matched.handlers[ j++ ]) && !event.isImmediatePropagationStopped() ) {

            //不存在命名空间，或者匹配的命名空间
            if ( !event.namespace_re || event.namespace_re.test( handleObj.namespace ) ) {

                event.handleObj = handleObj;
                event.data = handleObj.data;
                //执行绑定函数
                ret = ( (jQuery.event.special[ handleObj.origType ] || {}).handle || handleObj.handler )
                        .apply( matched.elem, args );
                // 如果是return false， 阻止默认事件，阻止冒泡
                if ( ret !== undefined ) {
                    if ( (event.result = ret) === false ) {
                        event.preventDefault();
                        event.stopPropagation();
                    }
                }
            }
        }
    }

    // Call the postDispatch hook for the mapped type
    if ( special.postDispatch ) {
        special.postDispatch.call( this, event );
    }
    
    return event.result;
},