使用TypeScript扩展Object.prototype

Question

我目前正在开发TypeScript API，它需要一些绑定到Object原型（Object.prototype）的附加功能。

请考虑以下代码：

class Foo {

}

interface Object {
    GetFoo(): Foo;
    GetFooAsString(): string;
}

//This is problematic...
Object.prototype.GetFoo = function() {
    return new Foo();
    // Note, this line is just for testing...I don't want my function to just return a blank instance of Foo!
}

//This is ok.
Object.prototype.GetFooAsString = function () {
    return this.GetFoo().toString();
}

您可能想直接在Playground尝试这个。

如您所见，我有一个名为Foo的类（不是我将使用的实际对象名）。 我还扩展了Object接口以包含两个新函数。 最后，我已经针对prototype实现了这些功能（这些功能在纯JavaScript中运行，只是抱怨的TypeScript）。

我在其中注释“ //这是有问题的...... ”TypeScript用红色波浪形突出显示，并显示以下错误：

Cannot convert '() => Foo' to '{ (): Foo; (): Foo; (): Foo; (): Foo; (): Foo; (): Foo; (): Foo; (): Foo; (): Foo; (): Foo; (): Foo; (): Foo; (): Foo; (): Foo; (): Foo; (): Foo; (): Foo; (): Foo; (): Foo; (): Foo; (): Foo; (): Foo; (): Foo; (): Foo; (): Foo; (): Foo; (): Foo; (): Foo; (): Foo; (): Foo; (): Foo; (): Foo; (): Foo; (): Foo; (): Foo; (): Foo; (): Foo; (): Foo; (): Foo; (): Foo; (): Foo; (): Foo; (): Foo; (): Foo; (): Foo; (): Foo; (): Foo; (): Foo; (): Foo; (): Foo; (): Foo; (): Foo; (): Foo; (): Foo; (): Foo; (): Foo; (): Foo; (): Foo; }': Call signatures of types '() => Foo' and '{ (): Foo; (): Foo; (): Foo; (): Foo; (): Foo; (): Foo; (): Foo; (): Foo; (): Foo; (): Foo; (): Foo; (): Foo; (): Foo; (): Foo; (): Foo; (): Foo; (): Foo; (): Foo; (): Foo; (): Foo; (): Foo; (): Foo; (): Foo; (): Foo; (): Foo; (): Foo; (): Foo; (): Foo; (): Foo; (): Foo; (): Foo; (): Foo; (): Foo; (): Foo; (): Foo; (): Foo; (): Foo; (): Foo; (): Foo; (): Foo; (): Foo; (): Foo; (): Foo; (): Foo; (): Foo; (): Foo; (): Foo; (): Foo; (): Foo; (): Foo; (): Foo; (): Foo; (): Foo; (): Foo; (): Foo; (): Foo; (): Foo; (): Foo; }' are incompatible
() => Foo

要么这只是一个TypeScript错误（我知道它仍处于开发阶段，所以很多错误需要解决，我已经在CodePlex上说明了一些），或者，我遗漏了一些东西。

为什么我会遇到这个问题？

如果它不是TypeScript错误，我该如何解决这个问题？

Answer 1

我曾经有过：

// See if an array contains an object
Array.prototype.contains = function (obj) {
    var i = this.length;
    while (i--) {
        if (this[i] === obj) {
            return true;
        }
    }
    return false;
}

为了使用typescript编译代码，我添加了以下行：

interface Array {
    contains(obj: Object): boolean;
}

谢谢basarat ！

Answer 2

这个错误在TS 0.9.0 alpha中修复，如下所示：

操场仍在运行0.8.3。

这基本上是因为某些关键接口（Object，Number，String）等上的方法被缓存为性能优化。

如果你运行这个。 第一次加载时您将看不到该错误。 试试吧 。

一旦你对该代码进行编辑，解析器就会再次遍历代码，并且由于它缓存了旧的接口定义，因此会看到重复的函数定义，然后会有效地破坏。 您对该文件所做的编辑越多，错误语句就越复杂。

Answer 3

我已经以相同的方式扩展了阵列，并且当一个派对正在使用for i in ...时候面对一个大问题for i in ...来循环它。 现在你无法控制每个第三方代码，这些错误可能真的很烦人，所以我建议一个更好的aprocach：

interface Array<T> {
   crandom(): T;
}

/** Retrieve a random element from the list */
 Object.defineProperty(Array.prototype, 'crandom', { value: function() {

    let index = Math.floor(Math.random() * this.length);

    return this[index];
}
});

现在通过使用Object.defineProperty您的新属性将不会被枚举，并且是安全的。 上面的代码几乎给出了数组中的随机元素。 我又做了一个从数组中弹出一个随机元素：

Object.defineProperty(Array.prototype, 'popRandom', { value: function() {

    let index = Math.floor(Math.random() * this.length);

    let result = this[index];
    this.splice(index, 1);

    return result;
}
});

使用Object.defineProperty您可以更好地控制此创建，也可以添加其他限制。