node.js中的emitter.emit方法使用说明

方法说明：

发射event事件，传递若干可选参数到事件监听器的参数表。

语法：

emitter.emit(event, [arg1], [arg2], […])

接收参数：

event                      事件类型

arg1 ~ argN           传递的参数(多个)

例子：

var  events = require(‘events’);
var emitter = new events.EventEmitter();
 
emitter.on(‘someEvent’, function(arg1, arg2){
    console.log(‘listener1’, arg1, arg2);
})
 
emitter.on(‘someEvent’, function(arg1, arg2){
    console.log(‘listener2’, arg1, arg2);
})
 
emitter.emit(‘someEvent’, ‘byvoid’, 1991);

源码：

EventEmitter.prototype.emit = function(type) {
  var er, handler, len, args, i, listeners;
  if (!this._events)
    this._events = {};
  // If there is no ‘error’ event listener then throw.
  if (type === ‘error’) {
    if (!this._events.error ||
        (util.isObject(this._events.error) && !this._events.error.length)) {
      er = arguments[1];
      if (this.domain) {
        if (!er) er = new TypeError(‘Uncaught, unspecified “error” event.’);
        er.domainEmitter = this;
        er.domain = this.domain;
        er.domainThrown = false;
        this.domain.emit(‘error’, er);
      } else if (er instanceof Error) {
        throw er; // Unhandled ‘error’ event
      } else {
        throw TypeError(‘Uncaught, unspecified “error” event.’);
      }
      return false;
    }
  }
  handler = this._events[type];
  if (util.isUndefined(handler))
    return false;
  if (this.domain && this !== process)
    this.domain.enter();
  if (util.isFunction(handler)) {
    switch (arguments.length) {
      // fast cases
      case 1:
        handler.call(this);