Cách hiểu mã JavaScript được tạo bởi từ khóa 'extends` của CoffeeScript

Question

Đây là mã JavaScript được tạo bởi từ khóa extends của CoffeeScript. Làm thế nào các chuỗi nguyên mẫu được thiết lập?

var __hasProp = Object.prototype.hasOwnProperty, 
__extends = function(child, parent) { 
    for (var key in parent) { 
     if (__hasProp.call(parent, key)) child[key] = parent[key]; 
    } 
    function ctor() { this.constructor = child; } 
    ctor.prototype = parent.prototype; 
    child.prototype = new ctor; 
    child.__super__ = parent.prototype; 
    return child; 
}; 

Answer 1

var __hasProp = Object.prototype.hasOwnProperty, 
__extends = function(child, parent) { 
    // Copy "static" attributes from the parent constructor to the child constructor 
    for (var key in parent) { 
     if (__hasProp.call(parent, key)) child[key] = parent[key]; 
    } 
    // This is the surrogate constructor, used so you don't need 
    // to instantiate an instance of the parent just to setup the prototype chain 
    // the statement in the surrogate constructor properly attaches 
    // the constructor property to object 
    function ctor() { this.constructor = child; } 
    // Attach the parent's prototype to the surrogate constructor 
    ctor.prototype = parent.prototype; 
    // This is setting up the chain, attaching an instance of a constructor whose 
    // prototype is set to the parent to the prototype property of the child 
    // In naive implementations, this would be child.prototype = new parent(); 
    child.prototype = new ctor; 
    // Allows access to the parent from user code, and used by the `super` keyword 
    child.__super__ = parent.prototype; 
    return child; 
}; 

Xem http://js-bits.blogspot.com/2010/08/javascript-inheritance-done-right.html (bài viết trên blog của riêng tôi)