type KeyOf<T> = keyof T;

class SomeClass<T, R> {
  onlyTFieldsAllowed = new Map<KeyOf<T>, R>();
}

class A {
  myField = 'myField';
}

const some = new SomeClass<A, any>();

some.onlyTFieldsAllowed.set('myField', 'WORKS');
some.onlyTFieldsAllowed.set('noneField', 'Not Allowed!');

var stuff: { [key: string]: string; } = {};
stuff['a'] = ''; // ok
stuff['a'] = 4;  // error

// ... or, if you're using this a lot and don't want to type so much ...
interface StringMap { [key: string]: string; }
var stuff2: StringMap = { };
// same as above

interface AgeMap {
    [name: string]: number
}

const friendsAges: AgeMap = {
    "Sandy": 34,
    "Joe": 28,
    "Sarah": 30,
    "Michelle": "fifty", // ERROR! Type 'string' is not assignable to type 'number'.
};

在这里，接口AgeMap强制键为字符串，值为数字。关键字名称可以是任何标识符，应该用于建议接口/类型的语法。

你可以使用类似的语法来强制一个对象对union类型中的每个条目都有一个键:

type DayOfTheWeek = "sunday" | "monday" | "tuesday" | "wednesday" | "thursday" | "friday" | "saturday";

type ChoresMap = { [day in DayOfTheWeek]: string };

const chores: ChoresMap = { // ERROR! Property 'saturday' is missing in type '...'
    "sunday": "do the dishes",
    "monday": "walk the dog",
    "tuesday": "water the plants",
    "wednesday": "take out the trash",
    "thursday": "clean your room",
    "friday": "mow the lawn",
};

当然，您也可以将其设置为泛型类型!

type DayOfTheWeek = "sunday" | "monday" | "tuesday" | "wednesday" | "thursday" | "friday" | "saturday";

type DayOfTheWeekMap<T> = { [day in DayOfTheWeek]: T };

const chores: DayOfTheWeekMap<string> = {
    "sunday": "do the dishes",
    "monday": "walk the dog",
    "tuesday": "water the plants",
    "wednesday": "take out the trash",
    "thursday": "clean your room",
    "friday": "mow the lawn",
    "saturday": "relax",
};

const workDays: DayOfTheWeekMap<boolean> = {
    "sunday": false,
    "monday": true,
    "tuesday": true,
    "wednesday": true,
    "thursday": true,
    "friday": true,
    "saturday": false,
};

10.10.2018更新: 看看下面@dracstaxi的答案——现在有一个内置的类型Record，它可以帮你完成大部分工作。

1.2.2020更新: 我已经完全从我的回答中删除了预先制作的映射接口。@dracstaxi的回答让他们完全无关紧要。如果您仍然想使用它们，请检查编辑历史记录。

定义接口

interface Settings {
  lang: 'en' | 'da';
  welcome: boolean;
}

强制键为设置界面的特定键

private setSettings(key: keyof Settings, value: any) {
   // Update settings key
}

一个快速更新:自Typescript 2.1以来，有一个内置的类型Record<T, K>，它的作用类似于字典。

在这种情况下，你可以这样声明:

var stuff: Record<string, any> = {};

你也可以通过联合文字类型来限制/指定潜在的键:

var stuff: Record<'a'|'b'|'c', string|boolean> = {};

下面是一个使用文档中的record类型的更通用的例子:

// For every properties K of type T, transform it to U
function mapObject<K extends string, T, U>(obj: Record<K, T>, f: (x: T) => U): Record<K, U>

const names = { foo: "hello", bar: "world", baz: "bye" };
const lengths = mapObject(names, s => s.length);  // { foo: number, bar: number, baz: number }

TypeScript 2.1文档记录<T, K>

我认为使用{[key: T]: K}的唯一缺点是，你可以编码关于你使用什么类型的键来代替“key”的有用信息，例如，如果你的对象只有质键，你可以这样提示:{[prime: number]: yourType}。

下面是我写的一个正则表达式来帮助这些转换。这只会转换标签为“key”的情况。要转换其他标签，只需更改第一个捕获组:

查找： \{\s*\[（key）\s*（+\s*：\s*（\w+）\s*\]\s*：\s*（[^\}]+？）\s*;？\s*\}

替换:记录<$ 2，$ 3>

实际上有一个内置的实用程序记录:

    const record: Record<string, string> = {};
    record['a'] = 'b';
    record[1] = 'c'; // leads to typescript error
    record['d'] = 1; // leads to typescript error