从Typescript 2.1开始，enum中的字符串键都是强类型的。Keyof typeof用于获取可用字符串键的信息(1):

enum Color{
    Red, Green
}

let typedColor: Color = Color.Green;
let typedColorString: keyof typeof Color = "Green";

// Error "Black is not assignable ..." (indexing using Color["Black"] will return undefined runtime)
typedColorString = "Black";

// Error "Type 'string' is not assignable ..." (indexing works runtime)
let letColorString = "Red";
typedColorString = letColorString;

// Works fine
typedColorString = "Red";

// Works fine
const constColorString = "Red";
typedColorString = constColorString

// Works fine (thanks @SergeyT)
let letColorString = "Red";
typedColorString = letColorString as keyof typeof Color;

typedColor = Color[typedColorString];

https://www.typescriptlang.org/docs/handbook/advanced-types.html#index-types

以这种方式创建的枚举被编译成一个对象，该对象同时存储正向(名称->值)和反向(值->名称)映射。从这张chrome devtools截图中我们可以看到:

下面是一个关于对偶映射如何工作以及如何从一个映射转换到另一个映射的例子:

enum Color{
    Red, Green
}
// To Number
var greenNr: number = Color['Green'];
console.log(greenNr); // logs 1

// To String
var greenString: string = Color[Color['Green']];  // or Color[Color[1]
console.log(greenString); // logs Green

// In your example

// recieve as Color.green instead of the string green
var green: string = Color[Color.Green];  

// obtain the enum number value which corresponds to the Color.green property
var color: Color = (<any>Color)[green];  

console.log(color); // logs 1

如果您为枚举提供字符串值，则直接强制转换可以很好地工作。

enum Color {
  Green = "Green",
  Red = "Red"
}

const color = "Green";
const colorEnum = color as Color;

如果你正在处理TypeScript 4.1+和字符串enum，并且你想要一个简单的具有编译时和运行时安全的字符串到enum转换器，下面的工作很好:

export const asEnum = <
  T extends { [key: string]: string },
  K extends keyof T & string
>(
  enumObject: T,
  value: `${T[K]}`
): T[K] => {
  if (Object.values(enumObject).includes(value)) {
    return (value as unknown) as T[K];
  } else {
    throw new Error('Value provided was not found in Enum');
  }
};

enum Test {
  hey = 'HEY',
}

const test1 = asEnum(Test, 'HEY');   // no complaints here
const test2 = asEnum(Test, 'HE');    // compile-time error
const test3 = asEnum(Test, 'HE' as any); // run-time error

从Typescript 2.1开始，enum中的字符串键都是强类型的。Keyof typeof用于获取可用字符串键的信息(1):

enum Color{
    Red, Green
}

let typedColor: Color = Color.Green;
let typedColorString: keyof typeof Color = "Green";

// Error "Black is not assignable ..." (indexing using Color["Black"] will return undefined runtime)
typedColorString = "Black";

// Error "Type 'string' is not assignable ..." (indexing works runtime)
let letColorString = "Red";
typedColorString = letColorString;

// Works fine
typedColorString = "Red";

// Works fine
const constColorString = "Red";
typedColorString = constColorString

// Works fine (thanks @SergeyT)
let letColorString = "Red";
typedColorString = letColorString as keyof typeof Color;

typedColor = Color[typedColorString];

https://www.typescriptlang.org/docs/handbook/advanced-types.html#index-types

如果TypeScript编译器知道变量的类型是字符串，那么这是可行的:

let colorName : string = "Green";
let color : Color = Color[colorName];

否则，你应该显式地将其转换为字符串(以避免编译器警告):

let colorName : any = "Green";
let color : Color = Color["" + colorName];

在运行时，两个解决方案都可以工作。