Backbone的 listenTo 和 on

使用情景区别

listenTo用于监听自身意外的对象

on用于监听自身

listenTo和on中的回调函数里的this的区别

listener.listenTo(object, 'eventName', function(){

    //此处的this指向listener

})

object.on('eventName', function(){

    //此处的this指向object

})

object.on('eventName', function(){

    //此处的this指向context

}, context)

触发顺序

当存在同名事件时,会按定义顺序执行,on和listenTo定义的事件会处在同一队列中

若监听了all事件,则触发任意事件都将会在执行完相应回调后执行all事件的回调,  all事件的监听会传递一个参数,该参数为事件名字

demo

                var a = {type: "I'm listening"}, b = {type: "I'm listened"};
                 _.extend(a, Backbone.Events);
                 _.extend(b, Backbone.Events);
                 b.on('onNoContext', function(){
                     console.log('trigger onNoContext');
                     console.log(this.type);
                 });
                 b.on('onContext', function(){
                     console.log('trigger onContext');
                     console.log(this.type);
                 }, a);
                 a.listenTo(b, 'listened', function(){
                     console.log('trigger listened');
                     console.log(this.type);
                 });
                 b.on('all', function(){
                     console.log('trigger on all');
                 });
                 a.listenTo(b,'all', function(){
                     console.log('trigger listen all');
                 });

                 console.log('###b.trigger("all")###');
                 b.trigger('all');
                 console.log('###b.trigger("onNoContext")###');
                 b.trigger('onNoContext');
                 console.log('###b.trigger("onContext")###');
                 b.trigger('onContext');
                 console.log('###b.trigger("listened")###');
                 b.trigger('listened');

运行结果:

1  ###b.trigger("all")###
2  trigger on all
3  trigger listen all
4  trigger on all
5  trigger listen all
6  ###b.trigger("onNoContext")###
7  trigger onNoContext
8  I'm listened
9  trigger on all
10 trigger listen all
11 ###b.trigger("onContext")###
12 trigger onContext
13 I'm listening
14 trigger on all
15 trigger listen all
16 ###b.trigger("listened")###
17 trigger listened
18 I'm listening
19 trigger on all
20 trigger listen all