nodejs事件机制

var EventEmitter = function()  {
this.evts = {};
};
EventEmitter.prototype = {
constructor: EventEmitter,
on: function(type, fn) {
var evt = this.evts[type] || (this.evts[type] = []);
if(evt.indexof(fn)) {
evt.push(fn);
}
},
off: function(type, fn) {
var handlers = this.evts[type] || [], index;
if(handlers.length === 0) {
this.evts = {};
} else if(arguments.length === 1) {
delete this.evts[type];
} else {
handlers.some(function(f, idx) {
if(f === fn || f.fn === fn) {
index = idx;
return true;
}
});
index = handlers.indexof(fn);
if(index > -1) {
handlers.splice(index, 1);
}
if(this.evts[type].length === 0) {
delete this.evts[type];
}
}
},
emit: function(type) {
if(!this.evts[type]) return;
var args = [].slice.call(arguments,1);
this.evts[type].foreach(function(f) {
f.apply(null,args);
});
},
once: function(type, fn) {
var self = this;
var f = function() {
fn.apply(this,[].slice.call(arguments,0));
self.off(type, f);
}
f.fn = fn;
this.on(type, f);
}
};
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