我不明白这个库如何使 NS var 在全局命名空间中可访问，因为它是用 var 声明的，你能解释一下吗。
更新:如果 Ns 不是全局的，那么这样做的目的是什么 var NS = namespace = {}; ？
http://blog.stephenrushing.com/index.php/javascript/custom-events-in-javascript/
(function () {
var NS = namespace = {};
var EVENTS = NS.events = {};
var eventify = EVENTS.eventify = function (target1, targetN) {
for (var t = 0; t < arguments.length; t++) {
var target = arguments[t];
if (!target.__listeners) {
if (!target.events) target.events = {};
target.__listeners = {};
target.dispatchEvent = function (eventType, eventData) {
if (this.events[eventType]) this.events[eventType].dispatch(this, eventData);
};
target.addEventListener = function (eventType, callback, bubbles) {
return new EVENTS.Listener(this, eventType, callback, bubbles);
};
target.removeEventListener = function (eventType, callback) {
var listeners = this.__listeners[eventType];
for (var l = 0; listeners && l < listeners.length; l++)
if (listeners[l] === callback || listeners[l].callback === callback) listeners.splice(l, 1);
};
}
}
}
var Event = EVENTS.Event = function (type) {
this.type = type;
this.history = [];
}
Event.prototype = {
bubbleTo: null,
currentTarget: null,
dispatch: function (target, eventData, currentTarget) {
this.target = target;
this.currentTarget = currentTarget || target;
var timeStamp = new Date();
this.timeStamp = timeStamp;
this._stopProp = false;
if (!currentTarget) {
var histObj = {
eventData: eventData,
timeStamp: timeStamp
};
} else {
var histObj = currentTarget.events[this.type].history[currentTarget.events[this.type].history.length - 1];
}
histObj.target = target;
histObj.currentTarget = currentTarget || target;
this.history.push(histObj);
var listeners = target.__listeners[this.type],
result;
for (var l = 0; listeners && l < listeners.length; l++) {
var listener = listeners[l];
if (eventData) result = listener.callback.call(target, this, eventData);
else result = listener.callback.call(target, this);
if (typeof (result) !== "undefined" && result !== null) this.result = result;
if (this._stopImmProp) break;
}
if (this.bubbleTo !== null && !this._stopProp) this.bubbleTo.events[this.type].dispatch(this.bubbleTo, eventData, this.currentTarget);
},
result: true,
_stopImmProp: false,
stopImmediatePropagation: function () {
this._stopImmProp = true
},
_stopProp: false,
stopPropagation: function () {
this._stopProp = true
},
target: null,
type: null,
history: null
}
var Listener = EVENTS.Listener = function (target, eventType, callback, bubbles) {
this.target = target;
this.callback = callback;
this.bubbles = (bubbles !== null) ? bubbles : true;
if (!target.events[eventType]) target.events[eventType] = this.event = new EVENTS.Event(eventType);
this.event = target.events[eventType];
if (!target.__listeners[eventType]) target.__listeners[eventType] = [];
target.__listeners[eventType].push(this);
}
Listener.prototype = {
bubbles: true,
callback: function (evt, data) {},
remove: function () {
var idx = Array.indexOf(this.target.__listeners[this.event.type], this);
this.target.__listeners[this.event.type].splice(idx, 1);
delete this;
},
event: null,
target: null
}
})();
最佳答案
NS 没有理由是全局的(它不是，在 Chrome 中测试)。然而，namespace 将会是，因为链式赋值总是会这样做(因此在 JS 中应该避免，除非赋值给之前声明的变量)。
var NS = namespace = {};
执行为:
namespace = {};
var NS = namespace;
更新
从博文来看，将“命名空间”声明为全局是有意的。
因此，该行的“有用性”主要是声明一个全局命名空间对象(namespace - 在我看来，这应该明确地完成，以表明其意图确实是使其全局化)。
... 和“同时”，创建对它的本地简短引用 (NS)。除了它很短之外，从理论上讲，在他的库代码的其余部分中引用这个局部变量比 window 的“全局”属性(namespace 确实是 window.namespace).
在这种情况下似乎令人困惑的一点是，在他的博客中，他将全局 namespace 对象称为 ns(请参阅“对于此示例， ...”)。换句话说，就博客文章而言，该行实际上是:
var NS = ns = {}; // which wouldn't exactly make its intent more clear.
关于JavaScript 匿名函数 : how is this variable exposed in global namespace，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/9080542/