功能的定制原型链 [英] Custom prototype chain for a function

问题描述

我很好奇我是否可以将一个对象包含到函数原型链中。我的意思是：

I am just curious whether I can include an object into function prototype chain. What I mean:

var test = function() { return 'a'; };

console.log(test.bind(this)); // return new bound function

// changing the prototype
// in console the prototype is really set as needed
// test => new object => function prototype => Object prototype
var F = function() {};
F.prototype = Function.prototype;
test.prototype = new F();

console.log(test.bind()); // this still works and returns new bound function

test.prototype.bind = function() {
    return 'test';
};

console.log(test.bind()); // this does not work as expected -> returns new bound function instead of 'test'. When I do delete Function.prototype.bind, then console.log(test.bind) returns undefined

推荐答案

您有一个函数 test 。它是 Function 的实例，并继承自 Function.prototype ，因此您可以调用 test例如。.bind。

You have a function test. It is a instanceof Function, and inherits from Function.prototype so that you can call test.bind for example.

然后，将函数的 prototype属性设置为从 Function继承的对象.prototype 。这意味着 test 的所有实例都将从该对象（以及Function.prototype）继承：

Then you set the "prototype" property of your function to an object inheriting from Function.prototype. That means that all instances of test will inherit from that object (and from Function.prototype):

var t = new test;
t instanceof test; // => true
t instanceof Function; // => true

然后，您覆盖自定义原型对象上的test属性。您这样做确实很不错，因为Function方法只能在函数（即可调用对象）上调用：

Then you overwrite the test property on your custom prototype object. You do good to do so, because Function methods should only be called on functions (i.e. callable objects):

>>> Function.prototype.bind.call({})
Unhandled Error: Function.prototype.bind: this object not callable

在使用 console.log 进行的测试中，您仅将函数方法应用于 test 函数，而不是实例。好，因为它们会失败。因此，我看不出为什么任何对象都应从 Function 继承-您不能构造不直接从 Function继承的函数。

In your tests with console.log you only apply the Function methods on your test function, not on instances of it. Good, because they'd fail. So, I can see no reason why any objects should inherit from Function - you can't construct functions that don't inherit directly from Function.

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