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