使用TypeScript扩展Object.prototype

Question

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

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();
}

您可能希望直接在Playground尝试此操作。

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称）。我还扩展了Object接口以包含两个新功能。最后，我针对prototype实现了这些功能（这些功能在纯JavaScript中运行，只是抱怨的TypeScript）。

我已注释“ //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，因此很多错误需要解决，我已经在CodePlex上说明了其中的一些），或者，我遗漏了一些东西。 / p>

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？

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，我添加了一行：

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

谢谢basarat！

Answer 2

此错误已在TS 0.9.0 alpha中修复，如下所示：

游乐场仍在运行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。

如果你运行它。第一次加载时您将看不到该错误。 Try It。

只要您对该代码进行编辑，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

我以相同的方式扩展了阵列，当派对使用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]; } }); 循环时，我遇到了一个大问题。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：

Object.defineProperty

现在使用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; } }); 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。我做了另一个，它从数组中弹出一个随机元素：

Object.defineProperty

fs.readFile("test.txt", function(err, data) { console.log( data ); }); 您可以更好地控制此创建，也可以添加其他限制。