设计模式学习（六）

5.发布--订阅模式

1. 首先要想好谁是发布者(比如上面的卖家)。
2. 然后给发布者添加一个缓存列表，用于存放回调函数来通知订阅者(比如上面的买家收藏了卖家的店铺，卖家通过收藏了该店铺的一个列表名单)。
3. 最后就是发布消息，发布者遍历这个缓存列表，依次触发里面存放的订阅者回调函数。

var event= {};(function (q) {     var topics = {}, // 回调函数存放的数组        subUid = -1;    // 发布方法 q.publish= function (topic, args) {         if (!topics[topic]) {            return false;        }         setTimeout(function () {            var subscribers = topics[topic],                len = subscribers ? subscribers.length : 0;             while (len--) {                subscribers[len].func(topic, args);            }        }, 0);         return true;     };    //订阅方法    q.subscribe = function (topic, func) {         if (!topics[topic]) {            topics[topic] = [];        }         var token = (++subUid).toString();        topics[topic].push({            token: token,            func: func        });        return token;    };    //退订方法    q.unsubscribe = function (token) {        for (var m in topics) {            if (topics[m]) {                for (var i = 0, j = topics[m].length; i < j; i++) {                    if (topics[m][i].token === token) {                        topics[m].splice(i, 1);                        return token;                    }                }            }        }        return false;    };} (event));

//发布

event.publish('aaa',111);

//订阅

event.subscribe('aaa', function (topics, data) {    console.log(data);});

var Event = (function(){ var clientList = {}, listen, trigger, remove; listen = function( key, fn ){ if ( !clientList[ key ] ){ clientList[ key ] = []; } clientList[ key ].push( fn ); }; trigger = function(){ var key = Array.prototype.shift.call( arguments ), fns = clientList[ key ]; if ( !fns || fns.length === 0 ){ return false; } for( var i = 0, fn; fn = fns[ i++ ]; ){ fn.apply( this, arguments ); } }; remove = function( key, fn ){ var fns = clientList[ key ]; if ( !fns ){ return false; } if ( !fn ){ fns && ( fns.length = 0 ); }else{ for ( var l = fns.length - 1; l >=0; l-- ){ var _fn = fns[ l ]; if ( _fn === fn ){ fns.splice( l, 1 ); } } } }; return { listen: listen, trigger: trigger, remove: remove } })(); var a = (function(){ var count = 0; var button = document.getElementById( 'count' ); button.onclick = function(){ Event.trigger( 'add', count++ ); } })(); var b = (function(){ var div = document.getElementById( 'show' ); Event.listen( 'add', function( count ){ div.innerHTML = count; }); })();