jQuery源码分析之jQuery.event.trigger及jQuery.Event十问
徐焱
问题1：jQuery.event.trigger常见调用方式有那些?
实例trigger方法
trigger: function( type, data ) {
return this.each(function() {
jQuery.event.trigger( type, data, this );//调用了jQuery.event.trigger方法
});
}triggerHandler: function( type, data ) {
var elem = this[0];
if ( elem ) {
return jQuery.event.trigger( type, data, elem, true );//jQuery.event.trigger调用
}
} jQuery.event.trigger("ajaxStart");//触发事件
jQuery.Event = function( src, props ) {
// Allow instantiation without the 'new' keyword
if ( !(this instanceof jQuery.Event) ) {//作用域安全的构造函数，所以即使没有new jQuery.Event也是相当于用new来构造对象的!
return new jQuery.Event( src, props );
}
// Event object
if ( src && src.type ) {//可以传入一个Event对象，也可以只是传入一个字符串如new jQuery.Event("click");
this.originalEvent = src;
this.type = src.type;
// Events bubbling up the document may have been marked as prevented
// by a handler lower down the tree; reflect the correct value.
this.isDefaultPrevented = src.defaultPrevented ||
src.defaultPrevented === undefined &&
// Support: IE < 9, Android < 4.0
src.returnValue === false ?
returnTrue :
returnFalse;
// Event type
} else {
this.type = src;
}
// Put explicitly provided properties onto the event object
if ( props ) {//第二个参数会被直接封装到this对象上面
jQuery.extend( this, props );
}
// Create a timestamp if incoming event doesn't have one
this.timeStamp = src && src.timeStamp || jQuery.now();
// Mark it as fixed
this[ jQuery.expando ] = true;//事件对象也有钥匙
};if ( src && src.type ) {//传入event对象
this.originalEvent = src;
this.type = src.type;
// Events bubbling up the document may have been marked as prevented
// by a handler lower down the tree; reflect the correct value.
this.isDefaultPrevented = src.defaultPrevented ||
src.defaultPrevented === undefined &&
// Support: IE < 9, Android < 4.0
src.returnValue === false ?
returnTrue :
returnFalse;
// Event type
} else {//传入字符串
this.type = src;
}if ( props ) {
jQuery.extend( this, props );
} this.timeStamp = src && src.timeStamp || jQuery.now();
// Mark it as fixed
this[ jQuery.expando ] = true;我们再来看看jQuery.Event的原型对象
正常情况下不阻止默认行为，不阻止冒泡
isDefaultPrevented: returnFalse,//默认行为不阻止
isPropagationStopped: returnFalse,//不阻止冒泡
isImmediatePropagationStopped: returnFalse,//不阻止冒泡preventDefault: function() {
var e = this.originalEvent;
this.isDefaultPrevented = returnTrue;
//调用了preventDefaule就会把修改isDefaultPrevented为true
if ( !e ) {
return;
}
// If preventDefault exists, run it on the original event
if ( e.preventDefault ) {
e.preventDefault();
// Support: IE
// Otherwise set the returnValue property of the original event to false
} else {
e.returnValue = false;
}
}stopPropagation: function() {
var e = this.originalEvent;
this.isPropagationStopped = returnTrue;//修改为已经阻止冒泡了
if ( !e ) {
return;
}
// If stopPropagation exists, run it on the original event
if ( e.stopPropagation ) {
e.stopPropagation();
}
// Support: IE
// Set the cancelBubble property of the original event to true
e.cancelBubble = true;
}stopImmediatePropagation: function() {
var e = this.originalEvent;
this.isImmediatePropagationStopped = returnTrue;//阻止冒泡行为
if ( e && e.stopImmediatePropagation ) {
e.stopImmediatePropagation();
}
this.stopPropagation();
} $("body").on("click",function(e)
{
console.log("body");
});
$("#parent").on("click",function(e)
{
console.log("click1");
});
$("#parent").on("click",function(e)
{
console.log("click2");
});我们调用一下stopPropagation:
$("body").on("click",function(e)
{
console.log("body");
});
$("#parent").on("click",function(e)
{
console.log("click1");
e.stopPropagation();//防止冒泡，但是两次click还是都会调用
});
$("#parent").on("click",function(e)
{
console.log("click2");
}); $("body").on("click",function(e)
{
console.log("body");
});
$("#parent").on("click",function(e)
{
console.log("click1");
e.stopImmediatePropagation();//防止冒泡,同时后面所有的click事件都不会被调用!
});
$("#parent").on("click",function(e)
{
console.log("click2");
});问题3：jQuery.event.trigger步骤是怎么样的?
第一步：看event对象是否有type属性和namespace属性，因为如果有namespace那么只能触发相同namespace属性的事件
eventPath = [ elem || document ],
//如果传入的event有type属性，那么获取该type属性
type = hasOwn.call( event, "type" ) ? event.type : event,
//如果有namespaces就获取namespaces属性!
namespaces = hasOwn.call( event, "namespace" ) ? event.namespace.split(".") : [];if ( elem.nodeType === 3 || elem.nodeType === 8 ) {
return;
}
// focus/blur morphs to focusin/out; ensure we're not firing them right now
// rfocusMorph = /^(?:focusinfocus|focusoutblur)$/,
if ( rfocusMorph.test( type + jQuery.event.triggered ) ) {
return;
} //如果type含有点好,那么第一项就是事件类型，如click，其余为命名空间!
if ( type.indexOf(".") >= 0 ) {
// Namespaced trigger; create a regexp to match event type in handle()
namespaces = type.split(".");
type = namespaces.shift();
namespaces.sort();
}
//如果type没有冒号，那么ontype就是在前面加上on
ontype = type.indexOf(":") < 0 && "on" + type;
// Caller can pass in a jQuery.Event object, Object, or just an event type string
//如果是jQuery.Event对象，那么是有仓库的，所以直接返回。如果不是jQuery.Event对象
//那么我们重新包装他为jQuery.Event对象，同时使得该对象具有原始event对象的所有信息!
event = event[ jQuery.expando ] ?
event :
new jQuery.Event( type, typeof event === "object" && event );
// Trigger bitmask: & 1 for native handlers; & 2 for jQuery (always true)
event.isTrigger = onlyHandlers ? 2 : 3;
//为event设置namespace属性,其中namespace属性就是用户自己传入的namespace属性，
//namespace_re属性是一个正则表达式，这个正则表达式通过用户自己传入的namespace来构建!
event.namespace = namespaces.join(".");
event.namespace_re = event.namespace ?
new RegExp( "(^|\\.)" + namespaces.join("\\.(?:.*\\.|)") + "(\\.|$)" ) :
null;
// Clean up the event in case it is being reused
//把event的result属性设置为undeined,以便回收使用!
event.result = undefined;
//设置target对象,如果没有target，那么表示target就是传入的参数,记住：这里是trigger不是用户行为触发的!
if ( !event.target ) {
event.target = elem;
}
// Clone any incoming data and prepend the event, creating the handler arg list
//如果没有传入data，那么data就是event对象，makeArray方法如果传入第二个参数表示把第一个data内容放入到event中
//所以如果传入了data那么data就是[event,data]！
data = data == null ?
[ event ] :
jQuery.makeArray( data, [ event ] );
// Allow special events to draw outside the lines
special = jQuery.event.special[ type ] || {};
//调用special自己有的trigger方法!
if ( !onlyHandlers && special.trigger && special.trigger.apply( elem, data ) === false ) {
return;
} // Determine event propagation path in advance, per W3C events spec (#9951)
// Bubble up to document, then to window; watch for a global ownerDocument var (#9724)
if ( !onlyHandlers && !special.noBubble && !jQuery.isWindow( elem ) ) {
bubbleType = special.delegateType || type;
// rfocusMorph = /^(?:focusinfocus|focusoutblur)$/
//也就是说bubbleType和type链接起来不是这种类型，那么获取父元素.因为focus和blur不冒泡!
if ( !rfocusMorph.test( bubbleType + type ) ) {
cur = cur.parentNode;
}
for ( ; cur; cur = cur.parentNode ) {
// eventPath = [ elem || document ]默认是document
//eventPath里面放入的是当前对象的所有父元素
eventPath.push( cur );
tmp = cur;
}
//给eventPath里面添加window的defaultView或者parentWindow
// Only add window if we got to document (e.g., not plain obj or detached DOM)
if ( tmp === (elem.ownerDocument || document) ) {
eventPath.push( tmp.defaultView || tmp.parentWindow || window );
}
} i = 0;
//获取传入的对象elem的每一个父元素，同时这个event没有停止冒泡!
while ( (cur = eventPath[i++]) && !event.isPropagationStopped() ) {
//如果event.type大于1那么就是bubbleType否则是bindType或者type本身
event.type = i > 1 ?
bubbleType :
special.bindType || type;
// jQuery handler
//不断获取当前元素和父元素的events对象，然后获取该对象的type类型对象，同时获取该对象的handle就是要执行的函数对象
handle = ( jQuery._data( cur, "events" ) || {} )[ event.type ] && jQuery._data( cur, "handle" );
//如果回调函数存在，那么调用该函数，传入的数据是data，也就是传入trigger函数传入的参数对象
if ( handle ) {
handle.apply( cur, data );
}
//本地handler对象，获取该对象的on事件
// Native handler
handle = ontype && cur[ ontype ];
//如果on事件存在，同时该对象能够保存数据也就是Element对象
if ( handle && handle.apply && jQuery.acceptData( cur ) ) {
//为event设置result值为handle调用后的结果
event.result = handle.apply( cur, data );
//如果返回是false，那么就直接停止冒泡
if ( event.result === false ) {
event.preventDefault();
}
}
}JS实例：
$("#n1").on("click",function(){console.log("n1 ")});
$("#n2").on("click",function(){console.log("n2 ")});
$("#n3").on("click",function(){console.log("n3 ")});
console.log($("#n3")[0].ownerDocument.defaultView);//Chrome是defaultView获取window对象，其它浏览器用parentWindow获取
window.οnclick=function(e)
{
console.log("window");
}HTML部分
<div id="n1">
<div id="n2">
<input type="checkbox" id="n3" href="www.baidu.com" style="display:inline-block;height:100px;width:100px;border:1px solid red;">
</div>
</div>
总之：调用的时候是获取eventPath中每一个DOM的特定类型的事件集合，同时调用该DOM的通用回调函数， 通用回调函数上下文为该DOM，该函数传入的唯一的参数是上面第四步构建的data对象!同时，如果调用的该类型事件还有ontype事件，那么ontype事件也需要调用， 调用函数上下文是当前DOM，参数是第四步构建的数据对象，但是如果ontype返回了false，那么就不会向父元素冒泡了!总之，按照jQuery.event.trigger来触发某一类特殊的事件的话， 他会触发该DOM所有父元素的同类的事件，包括on类型事件和通过其它方式绑定的事件!
最后一步：如果调用trigger方法，那么我需要触发对象的默认行为，这是为了和用户触发事件行为保持一致必须做的，如点击checkbox时候必须选中等
//设置type的值
event.type = type;
// If nobody prevented the default action, do it now
//如果不是一次调用，同时也没有阻止默认行为，那么我们还需要触发默认行为，这一点很重要!
if ( !onlyHandlers && !event.isDefaultPrevented() ) {
if ( (!special._default || special._default.apply( eventPath.pop(), data ) === false) &&
jQuery.acceptData( elem ) ) {
// Call a native DOM method on the target with the same name name as the event.
// Can't use an .isFunction() check here because IE6/7 fails that test.
// Don't do default actions on window, that's where global variables be (#6170)
if ( ontype && elem[ type ] && !jQuery.isWindow( elem ) ) {
//获取ontype事件句柄，从而使得在已经执行了type方法后不执行ontype事件!
// Don't re-trigger an onFOO event when we call its FOO() method
tmp = elem[ ontype ];
//将ontype句柄设置为null
if ( tmp ) {
elem[ ontype ] = null;
}
// Prevent re-triggering of the same event, since we already bubbled it above
//防止再次执行同样的事件，因为已经冒泡了!
jQuery.event.triggered = type;
try {
//执行type函数!
elem[ type ]();
} catch ( e ) {
// IE<9 dies on focus/blur to hidden element (#1486,#12518)
// only reproducible on winXP IE8 native, not IE9 in IE8 mode
}
//将trigger设置为null
jQuery.event.triggered = undefined;
if ( tmp ) {
elem[ ontype ] = tmp;
}
}
}
}
jQuery.event.trigger调用
trigger: function( event, data, elem, onlyHandlers ) //trigger第二个参数是数据，不过我们会把data最终转化为[event,data]类型
event.result = handle.apply( cur, data );//这里的data格式为[event,data]类型，cur是事件流当前所在的元素!
$("#n1").on("click",function(e,args){console.log(e);console.log(args);});//this就是当前DOM!
jQuery.event.trigger("click",{name:"qinliang"},$("#n1")[0]);//这时候你就知道，其实通过trigger调用的时候第一个参数是jQuery.Event对象，args是参数!还是上面的HTML结构
$("#n1").on("click",function(e,args){console.log(e);});
$("#n1")[0].οnclick=function(e)//通过这种方式添加事件是JS原生添加事件的方式，不是通过添加到DOM的events域上面的，通过elem[ontype]就可以访问的!
{
console.log("on click");
}
jQuery.event.trigger("click",{name:"qinliang"},$("#n1")[0]);如何阻止该事件的默认行为?
$("#n1").on("click",function(e,args){e.preventDefault();});//阻止默认行为
$("#n1")[0].οnclick=function(e)//该例子不管你怎么点击，checkbox都不会被选中!
{
console.log("on click");
}
jQuery.event.trigger("click",{name:"qinliang"},$("#n1")[0]);问题6：trigger调用能够阻止默认行为，那么trigger阻止了默认行为之后，用户手动触发事件是否能够再次触发事件?
解答:可以
$("#n1").on("click",function(e,args){e.preventDefault()});
$("#n1")[0].οnclick=function(e)
{
console.log("on click");
}
jQuery.event.trigger("click",{name:"qinliang"},$("#n1")[0]);问题7：jQuery.event.trigger是如何阻止默认行为的?
if ( !onlyHandlers && !event.isDefaultPrevented() ) {
if ( (!special._default || special._default.apply( eventPath.pop(), data ) === false) &&
jQuery.acceptData( elem ) ) {
// Call a native DOM method on the target with the same name name as the event.
// Can't use an .isFunction() check here because IE6/7 fails that test.
// Don't do default actions on window, that's where global variables be (#6170)
if ( ontype && elem[ type ] && !jQuery.isWindow( elem ) ) {
//获取ontype事件句柄，从而使得在已经执行了type方法后不执行ontype事件!
// Don't re-trigger an onFOO event when we call its FOO() method
tmp = elem[ ontype ];
//将ontype句柄设置为null
if ( tmp ) {
elem[ ontype ] = null;
}
// Prevent re-triggering of the same event, since we already bubbled it above
//防止再次执行同样的事件，因为已经冒泡了!
jQuery.event.triggered = type;
try {
//执行type函数!
elem[ type ]();
} catch ( e ) {
// IE<9 dies on focus/blur to hidden element (#1486,#12518)
// only reproducible on winXP IE8 native, not IE9 in IE8 mode
}
//将trigger设置为null
jQuery.event.triggered = undefined;
if ( tmp ) {
elem[ ontype ] = tmp;
}
}
}问题7：jQuery.event.triggered = type;在干嘛?
// Prevent re-triggering of the same event, since we already bubbled it above
//防止再次执行同样的事件，因为已经冒泡了!
jQuery.event.triggered = type;
try {
//执行type函数!
elem[ type ]();
} catch ( e ) {
// IE<9 dies on focus/blur to hidden element (#1486,#12518)
// only reproducible on winXP IE8 native, not IE9 in IE8 mode
}
//将trigger设置为null
jQuery.event.triggered = undefined;问题8：如果有些事件如blur,focus无法冒泡怎么办,这时候父元素应该触发什么类型事件?
$("#n1").on("focusin",function(e){console.log("n1 on focus");});
$("#n3").on("focus",function(e){console.log("on focus");});
jQuery.event.trigger("focus",{name:"qinliang"},$("#n3")[0]);问题9：如何调用自定义事件?
$("#n3").on("qinliang",function(e)
{
console.log("qinliang invoked!");
});
//自定义事件的执行，on方法把事件添加到events域下面，同时trigger把events域下面的同名事件
//拿出来执行!
jQuery.event.trigger("qinliang",{name:"qinliang"},$("#n3")[0]);trigger: function( event, data, elem, onlyHandlers ) {
var handle, ontype, cur,
bubbleType, special, tmp, i,
eventPath = [ elem || document ],
type = hasOwn.call( event, "type" ) ? event.type : event,
namespaces = hasOwn.call( event, "namespace" ) ? event.namespace.split(".") : [];
cur = tmp = elem = elem || document;
// Don't do events on text and comment nodes
if ( elem.nodeType === 3 || elem.nodeType === 8 ) {
return;
}
// focus/blur morphs to focusin/out; ensure we're not firing them right now
if ( rfocusMorph.test( type + jQuery.event.triggered ) ) {
return;
}
if ( type.indexOf(".") >= 0 ) {
// Namespaced trigger; create a regexp to match event type in handle()
namespaces = type.split(".");
type = namespaces.shift();
namespaces.sort();
}
ontype = type.indexOf(":") < 0 && "on" + type;
// Caller can pass in a jQuery.Event object, Object, or just an event type string
event = event[ jQuery.expando ] ?
event :
new jQuery.Event( type, typeof event === "object" && event );
// Trigger bitmask: & 1 for native handlers; & 2 for jQuery (always true)
event.isTrigger = onlyHandlers ? 2 : 3;
event.namespace = namespaces.join(".");
event.namespace_re = event.namespace ?
new RegExp( "(^|\\.)" + namespaces.join("\\.(?:.*\\.|)") + "(\\.|$)" ) :
null;
// Clean up the event in case it is being reused
event.result = undefined;
if ( !event.target ) {
event.target = elem;
}
// Clone any incoming data and prepend the event, creating the handler arg list
data = data == null ?
[ event ] :
jQuery.makeArray( data, [ event ] );
// Allow special events to draw outside the lines
special = jQuery.event.special[ type ] || {};
if ( !onlyHandlers && special.trigger && special.trigger.apply( elem, data ) === false ) {
return;
}
// Determine event propagation path in advance, per W3C events spec (#9951)
// Bubble up to document, then to window; watch for a global ownerDocument var (#9724)
if ( !onlyHandlers && !special.noBubble && !jQuery.isWindow( elem ) ) {
bubbleType = special.delegateType || type;
if ( !rfocusMorph.test( bubbleType + type ) ) {
cur = cur.parentNode;
}
for ( ; cur; cur = cur.parentNode ) {
eventPath.push( cur );
tmp = cur;
}
// Only add window if we got to document (e.g., not plain obj or detached DOM)
if ( tmp === (elem.ownerDocument || document) ) {
eventPath.push( tmp.defaultView || tmp.parentWindow || window );
}
}
// Fire handlers on the event path
i = 0;
while ( (cur = eventPath[i++]) && !event.isPropagationStopped() ) {
event.type = i > 1 ?
bubbleType :
special.bindType || type;
// jQuery handler
handle = ( jQuery._data( cur, "events" ) || {} )[ event.type ] && jQuery._data( cur, "handle" );
if ( handle ) {
handle.apply( cur, data );
}
// Native handler
handle = ontype && cur[ ontype ];
if ( handle && handle.apply && jQuery.acceptData( cur ) ) {
event.result = handle.apply( cur, data );
if ( event.result === false ) {
event.preventDefault();
}
}
}
event.type = type;
// If nobody prevented the default action, do it now
if ( !onlyHandlers && !event.isDefaultPrevented() ) {
if ( (!special._default || special._default.apply( eventPath.pop(), data ) === false) &&
jQuery.acceptData( elem ) ) {
// Call a native DOM method on the target with the same name name as the event.
// Can't use an .isFunction() check here because IE6/7 fails that test.
// Don't do default actions on window, that's where global variables be (#6170)
if ( ontype && elem[ type ] && !jQuery.isWindow( elem ) ) {
// Don't re-trigger an onFOO event when we call its FOO() method
tmp = elem[ ontype ];
if ( tmp ) {
elem[ ontype ] = null;
}
// Prevent re-triggering of the same event, since we already bubbled it above
jQuery.event.triggered = type;
try {
console.log(elem[type]);
elem[ type ]();
} catch ( e ) {
// IE<9 dies on focus/blur to hidden element (#1486,#12518)
// only reproducible on winXP IE8 native, not IE9 in IE8 mode
}
jQuery.event.triggered = undefined;
if ( tmp ) {
elem[ ontype ] = tmp;
}
}
}
}
return event.result;
}注意：最后的elem[type]如果你去alert出来会发现结果是function click(){[native code]}也就是说这里是为target对象调用默认方法，如果是checkbox就是表示选中，如果是超链接默认行为就是表示打开等!但是对于click方法来说，根据源码，如果你是triggerClick,那么根本不会打开超链接，其它元素默认事件会触发，唯独超链接的click不会!
上面你必须要弄清楚：
function A( event,data ){
alert( 'A' +data.name);
}
function B( event,data ){
alert( 'B' +data.name);
}
function C( event,data ){
alert( 'C' +data.name);
}
var $btn1 = $("#btn1");
// 为btn1元素的click事件绑定事件处理函数
$btn1.bind( "click.foo.bar", A );
$btn1.bind( "click.test.foo", B );
$btn1.bind( "click.test", C );
// 触发btn1的包含命名空间test的click事件
$btn1.trigger("click.foo",{name:"xxx"},$btn1); // 触发B、C
(2)那么当调用trigger的时候如何保证相应的namespace下的所有函数都会执行呢?这时候trigger中的namespace_re代码就起作用了，他会根据自己的命名空间创建相应的正则表达式，然后保存到event对象中!同时event会传递到handle方法中，然后传递到dispatch中，该方法中有一个判断 if ( !event.namespace_re || event.namespace_re.test( handleObj.namespace ) )这样就能够保证通过on方法添加的handleObj如果满足这个正则表达式就能够执行!如第一个handleObj是"foo.bar",第二个是"test.foo",第三个是"test"，于是用trigger的正则表达式去匹配，最后就会执行B和C!
(3)我们得出结论，通过点击触发事件和通过trigger触发事件本质上没有任何区别(除了click作用于a),都是调用相应元素的handle方法!该冒泡的时候也是会冒泡的!回调的时候会给相应的绑定的参数传递event对象和data对象!
(4)为什么我说上面trigger方法该冒泡的时候也会冒泡呢?如果子元素调用trigger("click.test")那么所有的父元素的"click"为什么不会执行呢?
$(document.getElementById("container")).on("click",function(){alert("invoked container!")})
$(document.getElementById("content")).on("click",function(event){alert("invoked content!"+event.type)})
//拿着上面所有的click事件类型
$(document.getElementById("content")).trigger("click.test");如果叫你设计一个触发一个对象的事件，你会怎么设计?
(1)获取该元素以及该元素所有的父元素，至于为什么用父元素是为了用于冒泡的!得到一个DOM集合!
(2)循环遍历DOM集合，获取每一个元素上面相应的事件，如果i<1获取绑定事件，否则获取冒泡事件!并且调用事件!
(3)循环结束以后，对target对象调用原生方法，使得他能够完成浏览器默认的动作，如checkbox就是选中，a就是打开链接!
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