令人困惑的JavaScript语句：“ var x = new this（）;” [英] Confusing JavaScript statement: "var x = new this();"

问题描述

我以为我了解JavaScript原型对象以及[[proto]]的概念，直到看到一些有关类继承的帖子。

I thought I understood the concept of the JavaScript prototype object, as well as [[proto]] until I saw a few posts regarding class inheritance.

首先， http://amix.dk/blog/viewEntry/19038

请参阅实现部分：

var parent = new this('no_init');

还有John Resig出色博客上的简单JavaScript继承。

And also "Simple JavaScript Inheritance" on John Resig's great blog.

var prototype = new this();

new this（）是什么？实际上意思？

这句话对我来说毫无意义，因为据我了解， this 指向对象而不是构造函数功能。我还尝试过在Firebug中测试语句以弄清楚这一点，而我收到的只是语法错误。

This statement makes no sense to me because my understand has been that this points to an object and not a constructor function. I've also tried testing statements in Firebug to figure this one out and all I receive is syntax errors.

我的头已经完全旋转了。

My head has gone off into a complete spin.

有人可以详细解释一下吗？

Could someone please explain this in detail?

推荐答案

AJS.Class 有效地*翻译为：

var Person = new AJS.Class({
    init: function(name) {
        this.name = name;
        Person.count++;
    },
    getName: function() {
        return this.name;
    }
});
Person.count = 0;

为此：

var Person = function (name) {
    this.name = name;
    Person.count++;
};

Person.prototype = {
    getName: function() {
        return this.name;
    }
};

Person.extend = AJS.Class.prototype.extend;
Person.implement = AJS.Class.prototype.implement;

Person.count = 0;

因此，在这种情况下， this AJS.Class.prototype.extend 是指 Person ，因为：

Therefore, in this case, this in AJS.Class.prototype.extend refers to Person, because:

Person.extend(...);
// is the same as
Person.extend.call(Person, ...);
// is the same as
AJS.Class.prototype.extend.call(Person, ...);

*在很多情况下，我都不会忽略；重写是为了简化理解问题。

* There are a lot of cases I don't go over; this rewrite is for simplicity in understanding the problem.

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