之前写了篇文章《原生javascript实现类似jquery on方法的行为监听》比较浅显，能够简单的使用场景。
这里的自定义事件指的是区别javascript默认的与DOM交互的事件，比如click，mouseover,change等，有时候我们需要监听某一行为是否发生，很显然默认的行为不够用，比如一个场景。我们写好了tab切换，点击后请求加载隐藏标签的内容。
tab切换是非常常用的一个功能，通常会写成组件，如果每次把请求写在组件里肯定对组件拓展和耦合性有影响。这时候我们可以在组件里自定义一个事件广播，在其他地方监听这个广播再执行请求就可以避免了。
以上只是使用场景，下面是具体实现：
1、简易代码，基础功能：
<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <title>自定义事件</title> </head> <body> <button id="demo">点我吧</button> <script type="text/javascript"> function Observer(){ this._events={}; } Observer.prototype={ on:function(eName,fn,scope){ eName=eName.toLowerCase(); this._events[eName]=[]; this._events[eName].push({fn:fn||null,scope:scope||null}); }, fireEvent:function(){ var args=Array.prototype.slice.call(arguments);//将参数转为数组 var eName=args.shift().toLowerCase(); var list=this._events[eName]; for(var i=0;i<list.length;i++){ var dict=list[i]; var fn=dict.fn; var scope=dict.scope; fn.apply(scope||null,args);//注册事件执行 } } } var listener=new Observer(); listener.on("alert",function(name ,age){ console.log(name+":"+age); }); listener.on("aha",function(name ,age){ console.log("这是另外一个事件"+name+":"+age); }); var $btn=document.getElementById("demo") $btn.onclick=function(){ listener.fireEvent('aha', '彼岸花再开', 28); } </script> </body> </html>
有点类似jquery里面的on方法,$(ele).on(type,fn)。上面的on是注册一个事件，这个事件是一个对象，存储当前的事件名称和函数。fireEvent可以理解为释放，发射，监听事件。
完整的实现：
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>自定义事件</title>
</head>
<body>
<button id="demo">点我吧</button>
<script type="text/javascript">
function Observer() {
this._events = {};
}
Observer.prototype = {
constructor: this,
addEvent: function(eName, fn) {
if (typeof(eName) === "string" && typeof(fn) === "function") {
eName = eName.toLowerCase();
if (typeof(this._events[eName]) === "undefined") {
this._events[eName] = [fn];
} else {
this._events[eName].push(fn);
}
}
return this;
},
addEvents: function(obj) { //绑定多事件
obj = typeof(obj) === "object" ? obj : {};
for (var eName in obj) {
if (eName && typeof(obj[eName] === "function")) {
this.addEvent(eName, obj[eName]);
}
}
return this;
},
fireEvent: function(eName) { //触发事件
if (eName && this._events[eName]) {
var events = {
eName: eName,
target: this
};
for (var length = this._events[eName].length, start = 0; start < length; start++) {
this._events[eName][start].call(this, events);
}
}
return this;
},
fireEvents: function(array) {
if (array instanceof Array) {
for (var i = 0, len = array.length; i < len; i++) {
this.fireEvent(array[i]);
}
}
return this;
},
removeEvent: function(eName, key) { //删除绑定的事件
var eventsList = this._events[eName];
if (eventsList instanceof Array) {
if (typeof(key) === "function") {
for (var i = 0, len = eventsList.length; i < len; i++) {
if (eventsList[i] === key) {//移除其中某个事件
eventsList.splice(i, 1);
break;
}
}
} else if (key instanceof Array) {//移除某个事件下面多个函数
for (var lis = 0, lenkey = key.length; lis < lenkey; lis += 1) {
this.removeEvent(type, key[lenkey]);
}
} else {//直接移除事件下所有函数
delete this._events[eName];
}
}
return this;
},
removeEvents: function(params) {
if (params instanceof Array) {
for (var i = 0, length = params.length; i < length; i += 1) {
this.removeEvent(params[i]);
}
} else if (typeof params === "object") {
for (var type in params) {
this.removeEvent(type, params[type]);
}
}
return this;
}
}
var listeners = new Observer();
listeners.addEvents({
"once": function() {
alert("该事件只会出现一次！");
this.removeEvent("once");
},
"infinity": function() {
alert("每次点击页面，该事件都会！");
}
});
document.onclick = function(e) {
e = e || window.event;
var target = e.target || e.srcElement;
if (!target || !/button/i.test(target.tagName)) {
listeners.fireEvents(["once", "infinity"]);
}
};
</script>
</body>
</html>
换apply实现，细心的你是否发现其中的差别呢：
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>自定义事件</title>
</head>
<body>
<button id="demo">点我吧</button>
<script type="text/javascript">
function Observer() {
this._events = {};//存储事件对象
}
Observer.prototype = {
constructor: this,
addEvent: function(eName, fn) {//绑定事件
if (typeof(eName) === "string" && typeof(fn) === "function") {
eName = eName.toLowerCase();
if (typeof(this._events[eName]) === "undefined") {
this._events[eName] = [{//将事件函数绑定到事件名称
fn: fn
}];
} else {
this._events[eName].push({
fn: fn
});
}
}
return this;
},
addEvents: function(obj) { //绑定多事件
obj = typeof(obj) === "object" ? obj : {};
for (var eName in obj) {
if (eName && typeof(obj[eName] === "function")) {
this.addEvent(eName, obj[eName]);
}
}
return this;
},
fireEvent: function(eName) {//广播事件，射吧！
var args = Array.prototype.slice.call(arguments);//将参数转为数组
var eName = args.shift().toLowerCase();//第一个参数是事件名，这里需要除时间名之外的参数
var list = this._events[eName];
if(list instanceof Array){
for (var i = 0; i < list.length; i++) {
var dict = list[i];
var fn = dict.fn;
fn.apply(null, args);
}
}
return this;
},
fireEvents: function(array) {
if (array instanceof Array) {
for (var i = 0, len = array.length; i < len; i++) {
this.fireEvent(array[i]);
}
}
return this;
},
removeEvent: function(eName, key) {
var eventsList = this._events[eName];
if (eventsList instanceof Array) {
if (typeof(key) === "function") {
for (var i = 0, len = eventsList.length; i < len; i++) {
if (eventsList[i] === key) {
eventsList.splice(i, 1);
break;
}
}
} else if (key instanceof Array) {
for (var lis = 0, lenkey = key.length; lis < lenkey; lis += 1) {
this.removeEvent(type, key[lenkey]);
}
}else{
delete this._events[eName];
}
}
}
}
var listeners = new Observer();
listeners.addEvents({
"once": function() {
alert("该事件只会出现一次！");
listeners.removeEvent("once");
},
"infinity": function() {
alert("每次点击页面，该事件都会出现！");
}
});
document.onclick = function(e) {
e = e || window.event;
var target = e.target || e.srcElement;
if (!target || !/input|pre/i.test(target.tagName)) {
listeners.fireEvents(["once", "infinity"]);
}
};
</script>
</body>
</html>