爲什麼這樣的背景？

Question

爲什麼7行返回對象窗口？

爲什麼不是運動對象？

var sport = { 
caption: "2017", 
players : [{"name":"cat"},{"name":"dog"}] , 
show: function() { 
    this.players.forEach(function(entry) { 
     console.log(entry.name); 
     console.log(this);//window 
    }); 
} 
} 

sport.show(); 

https://jsfiddle.net/6qkj2byk/

Answer 1

this是指它在其中駐留的匿名功能，這將是窗口的範圍。

var sport = { 
 
    players: [1, 2, 3], 
 
    show: function() { 
 
    this.players.forEach(function(entry) { 
 
     console.log(entry); 
 
     
 
     // this refers to the scope of the anonymous function, which is window 
 
     console.log(this); 
 
    }); 
 
    } 
 
} 
 

 
//sport.show(); 
 

 

 
var sport2 = { 
 
    players: [3, 4, 5], 
 
    show: function() { 
 

 
    // this refers to the object scope in which it resides - 
 
    // in which case, that would be "sport2" 
 
    var self = this; 
 
    this.players.forEach(function(entry) { 
 
     console.log(entry); 
 

 
     // self is now synonymous with "this" in the sport2 scope. 
 
     console.log(self); 
 
    }); 
 
    } 
 
} 
 

 
sport2.show();

編輯：自可以在show功能本身的內部設置，沒有必要將它傳遞的醜陋的方式。感謝評論部分指出了這一點。