Question

在underscore.js code中，评论声明：

// Naked function reference for surrogate-prototype-swapping.
var Ctor = function(){};

什么是代理 - 原型交换？

或

我在哪里可以找到关于代理原型交换的文章/明确文档？

Answer 1

通过Blender的回答做到了。适合我级别的人。

虽然这不是一个真正的术语，但以下是对原始underscore.js代码进行更完整评论的替代原型交换的预期含义的细分。

// A function which will be used as a constructor function in order 
// to add a prototype to a new object. There is nothing special about
// this function, except how it will be used.
var Ctor = function(){};

// Create a shortcut to Object.create if it exists. Otherwise
// nativeCreate will be undefined
var nativeCreate = Object.create;

// An internal function that will use or act as a polyfill for
// Object.create, with some type checking built in.
var baseCreate = function(prototype) {
    // Check if the object passed to baseCreate is actually an object.
    // Otherwise simply return an object (from an object literal), 
    // because there is not a valid object to inherit from.
    if (!_.isObject(prototype)) return {};

    // If Object.create is implemented then return the value
    // returned by Object.create when the prototype parameter is
    // passed into it. If Object.create has already been
    // implemented there is no need to recreate it. Just return
    // its return value.
    if (nativeCreate) return nativeCreate(prototype);

    // If Object.create is not defined then Ctor comes into play.
    // The object passed to baseCreate is assigned to the prototype
    // of Ctor. This means when Ctor is called prototype will be
    // the prototype assigned to this (the keyword this).
    Ctor.prototype = prototype;
    // Because Ctor is called with the new keyword this (the
    // keyword this) is returned returned by Ctor. Thus, the
    // variable 'result' is assigned an object with a prototype
    // equal to baseCreate's parameter 'prototype'.
    var result = new Ctor;
    // Then to reset things Ctor.prototype is set to null.
    Ctor.prototype = null;
    // The newly created object, whose prototype is the object
    // passed to baseCreate is returned.
    return result;
};

Answer 2

“代理原型交换”（我怀疑这是一个真实的东西）是使用一个对象只分配给它的原型。该变量仅使用一次：

// Naked function reference for surrogate-prototype-swapping.
var Ctor = function(){};

var nativeCreate = Object.create;

// An internal function for creating a new object that inherits from another.
var baseCreate = function(prototype) {
    if (!_.isObject(prototype)) return {};

    if (nativeCreate) return nativeCreate(prototype);

    Ctor.prototype = prototype;
    var result = new Ctor;
    Ctor.prototype = null;
    return result;
};

用于制作Object.create的跨浏览器版本。您无法直接创建原型对象的新实例，因此您将原型对象作为其原型创建一个临时对象，并返回该实例。

什么是代理原型交换javascript？

2 个答案: