emitter 发布订阅参考好文：
// 源码 https://github.com/scottcorgan/tiny-emitter/blob/master/index.js
function E () {
// Keep this empty so it's easier to inherit from
// (via https://github.com/lipsmack from https://github.com/scottcorgan/tiny-emitter/issues/3)
}
E.prototype = {
on: function (name, callback, ctx) {
var e = this.e || (this.e = {});
(e[name] || (e[name] = [])).push({
fn: callback,
ctx: ctx
});
return this;
},
once: function (name, callback, ctx) {
var self = this;
function listener () {
self.off(name, listener);
callback.apply(ctx, arguments);
};
listener._ = callback
return this.on(name, listener, ctx);
},
emit: function (name) {
var data = [].slice.call(arguments, 1);
var evtArr = ((this.e || (this.e = {}))[name] || []).slice();
var i = 0;
var len = evtArr.length;
for (i; i < len; i++) {
evtArr[i].fn.apply(evtArr[i].ctx, data);
}
return this;
},
off: function (name, callback) {
var e = this.e || (this.e = {});
var evts = e[name];
var liveEvents = [];
if (evts && callback) {
for (var i = 0, len = evts.length; i < len; i++) {
if (evts[i].fn !== callback && evts[i].fn._ !== callback)
liveEvents.push(evts[i]);
}
}
// Remove event from queue to prevent memory leak
// Suggested by https://github.com/lazd
// Ref: https://github.com/scottcorgan/tiny-emitter/commit/c6ebfaa9bc973b33d110a84a307742b7cf94c953#commitcomment-5024910
(liveEvents.length)
? e[name] = liveEvents
: delete e[name];
return this;
}
};
module.exports = E;
module.exports.TinyEmitter = E;
mittmitt 和 tiny-emitter 的对比分析
on(type, handler)、off(type, [handler]) 和 emit(type, [evt]) 三个方法来注册、注销、派发事件emit
all 属性，可以拿到对应的事件类型和事件处理函数的映射对象，是一个 Map 不是 {}'*' 事件，可以调用 emitter.all.clear()清除所有事件tiny-emitter
e 属性可以拿到所有事件（需要看代码才知道）once 方法 并且 支持设置 this(指定上下文 ctx)addEventListenerMapcallapply