每周优秀代码赏析系列【二】----Jif

2011-10-30 12:06 【当耐特】阅读(3432) 评论(3) 编辑收藏举报

一.简介

Jif是一个轻量级的events，Jif提供了事件监听on、发送send和清空clear接口，我们可以为其扩展remove 等接口。

Jif也是观察者模式的一种优雅实现。

二.代码公布

下面就公布本周的优秀代码：

var Jif = function () {
    this._listeners = {};
};
 
Jif.prototype = (function (undefined) {
    return {
        on: function (event, callback) {
            if (this._listeners[event] === undefined) {
                this._listeners[event] = [];
            }
 
            this._listeners[event].push(callback);
        },
 
        clear: function (event, callback) {
            var listeners = this._listeners[event];
            var i = listeners.length;
 
            if (listeners === undefined) {
                throw new Error('Unknown event type: ' + event);
            }
 
            if (callback === undefined) {
                this._listeners[event] = [];
                return;
            }
 
            while (i > 0) {
                i -= 1;
                if (listeners[i] === callback) {
                    this._listeners[event].splice(i, 1);
                }
            }
        },
  
        send: function (event, msg) {
            var listeners = this._listeners[event];
            var i = listeners.length;
 
            if (listeners === undefined) {
                throw new Error('Unknown event type: ' + event);
            }
 
            while (i > 0) {
                i -= 1;
                listeners[i](msg);
            }
        }
    };
})();

三.用法

var events = new Jif();
//订阅天气
events.on('weather', function (weather) {
    alert('today is   ' + weather.condition);
});
//发布天气
events.send('weather', { condition: 'sunny' });