javascript - 什么是 JavaScript 中的 __proto__ 类型代理？

Question

使用 Backbone.js，我通过控制台记录了一个 Backbone.View.extend({}) 的实例，以找到要作为代理项的 __proto__ 类型。

var view = Backbone.View.extend({});
console.log(view);

这导致其 __proto__ 的类型为 Surrogate 的对象

__proto__: Surrogate

什么是代理？

Answer 1

Surrogate 是 Backbone 中的一个“助手”类，用于设置原型(prototype)链。查看源代码:

  // Helper function to correctly set up the prototype chain, for subclasses.
  // Similar to `goog.inherits`, but uses a hash of prototype properties and
  // class properties to be extended.
  var extend = function(protoProps, staticProps) {
    var parent = this;
    var child;

    // The constructor function for the new subclass is either defined by you
    // (the "constructor" property in your `extend` definition), or defaulted
    // by us to simply call the parent's constructor.
    if (protoProps && _.has(protoProps, 'constructor')) {
      child = protoProps.constructor;
    } else {
      child = function(){ parent.apply(this, arguments); };
    }

    // Add static properties to the constructor function, if supplied.
    _.extend(child, parent, staticProps);

    // Set the prototype chain to inherit from `parent`, without calling
    // `parent`'s constructor function.
    var Surrogate = function(){ this.constructor = child; };
    Surrogate.prototype = parent.prototype;
    child.prototype = new Surrogate;

    // Add prototype properties (instance properties) to the subclass,
    // if supplied.
    if (protoProps) _.extend(child.prototype, protoProps);

    // Set a convenience property in case the parent's prototype is needed
    // later.
    child.__super__ = parent.prototype;

    return child;
  };