对象文字中的范围链

Question

var x = 9;
var mod = {
    x: 81,
    assign: function(){
        this.x = 9;
        x = 3;
    },
    checkVars: function(){
        alert(x + " - " + this.x );
    }
};

mod.checkVars(); //9 - 81

mod.assign();
mod.checkVars(); //3 - 9

alert(x); //3

请解释范围链如何在这里设置自己.为什么范围解析为xin checkVars和assignskip对象mod？

Answer 1

我在你的程序中添加了一些评论:

var x = 9; // This is the *only* variable called x in your program
var mod = {
    x: 81, // this x refers to a property of mod also called x
    assign: function(){
        this.x = 9; // "this" refers to the object mod, this.x is the x property of mod
        x = 3; // x here refers to your variable called x
    },
    checkVars: function(){
        alert(x + " - " + this.x ); // same as above
    }
};

mod.checkVars(); //9 - 81

mod.assign();
mod.checkVars(); //3 - 9

alert(x); //3

换句话说,您的混淆与范围解析没有任何关系.无论何时引用x,您都指x的是在程序顶部定义的唯一一个变量.您提到的任何时候this.x,您指的是x在mod对象文字上定义的名为您的属性.

希望这有助于澄清事情!