原型实现的一个观察者模式

function Observer() {
    this.fns = [];
}
Observer.prototype = {
    subscribe: function (fn) {
        this.fns.push(fn);
    },
    unsubscribe: function (fn) {
        this.fns = this.fns.filter(
                        function (el) {
                            if (el !== fn) {
                                return el;
                            }
                        }
                    );
    },
    update: function (o, thisObj) {
        var scope = thisObj || window;
        this.fns.forEach(
                        function (el) {
                            el.call(scope, o);
                        }
                    );
    }
};

//测试
var o = new Observer;
var f1 = function (data) {
    console.log('Robbin: ' + data + ', 赶紧干活了！');
};

var f2 = function (data) {
    console.log('Randall: ' + data + ', 找他加点工资去！');
};

o.subscribe(f1);
o.subscribe(f2);

o.update("Tom回来了！")

//退订f1
o.unsubscribe(f1);
//再来验证
o.update("Tom回来了！");