How to create enum like type in TypeScript?

Solution 1:

TypeScript 0.9+ has a specification for enums:

enum AnimationType {
    BOUNCE,
    DROP,
}

The final comma is optional.

Solution 2:

As of TypeScript 0.9 (currently an alpha release) you can use the enum definition like this:

enum TShirtSize {
  Small,
  Medium,
  Large
}

var mySize = TShirtSize.Large;

By default, these enumerations will be assigned 0, 1 and 2 respectively. If you want to explicitly set these numbers, you can do so as part of the enum declaration.

Listing 6.2 Enumerations with explicit members

enum TShirtSize {
  Small = 3,
  Medium = 5,
  Large = 8
}

var mySize = TShirtSize.Large;

Both of these examples lifted directly out of TypeScript for JavaScript Programmers.

Note that this is different to the 0.8 specification. The 0.8 specification looked like this - but it was marked as experimental and likely to change, so you'll have to update any old code:

Disclaimer - this 0.8 example would be broken in newer versions of the TypeScript compiler.

enum TShirtSize {
  Small: 3,
  Medium: 5,
  Large: 8
}

var mySize = TShirtSize.Large;

Solution 3:

This is now part of the language. See TypeScriptLang.org > Basic Types > enum for the documentation on this. An excerpt from the documentation on how to use these enums:

enum Color {Red, Green, Blue};
var c: Color = Color.Green;

Or with manual backing numbers:

enum Color {Red = 1, Green = 2, Blue = 4};
var c: Color = Color.Green;

You can also go back to the enum name by using for example Color[2].

Here's an example of how this all goes together:

module myModule {
    export enum Color {Red, Green, Blue};

    export class MyClass {
        myColor: Color;

        constructor() {
            console.log(this.myColor);
            this.myColor = Color.Blue;
            console.log(this.myColor);
            console.log(Color[this.myColor]);
        }
    }
}

var foo = new myModule.MyClass();

This will log:

undefined  
2  
Blue

Because, at the time of writing this, the Typescript Playground will generate this code:

var myModule;
(function (myModule) {
    (function (Color) {
        Color[Color["Red"] = 0] = "Red";
        Color[Color["Green"] = 1] = "Green";
        Color[Color["Blue"] = 2] = "Blue";
    })(myModule.Color || (myModule.Color = {}));
    var Color = myModule.Color;
    ;
    var MyClass = (function () {
        function MyClass() {
            console.log(this.myColor);
            this.myColor = Color.Blue;
            console.log(this.myColor);
            console.log(Color[this.myColor]);
        }
        return MyClass;
    })();
    myModule.MyClass = MyClass;
})(myModule || (myModule = {}));
var foo = new myModule.MyClass();

Solution 4:

Just another note that you can a id/string enum with the following:

class EnumyObjects{
    public static BOUNCE={str:"Bounce",id:1};
    public static DROP={str:"Drop",id:2};
    public static FALL={str:"Fall",id:3};


}

Solution 5:

Update:

As noted by @iX3, Typescript 2.4 has support for enum strings.

See:Create an enum with string values in Typescript

Original answer:

For String member values, TypeScript only allows numbers as enum member values. But there are a few solutions/hacks you can implement;

Solution 1:

copied from: https://blog.rsuter.com/how-to-implement-an-enum-with-string-values-in-typescript/

There is a simple solution: Just cast the string literal to any before assigning:

export enum Language {
    English = <any>"English",
    German = <any>"German",
    French = <any>"French",
    Italian = <any>"Italian"
}

solution 2:

copied from: https://basarat.gitbooks.io/typescript/content/docs/types/literal-types.html

You can use a string literal as a type. For example:

let foo: 'Hello';

Here we have created a variable called foo that will only allow the literal value 'Hello' to be assigned to it. This is demonstrated below:

let foo: 'Hello';
foo = 'Bar'; // Error: "Bar" is not assignable to type "Hello"

They are not very useful on their own but can be combined in a type union to create a powerful (and useful) abstraction e.g.:

type CardinalDirection =
    "North"
    | "East"
    | "South"
    | "West";

function move(distance: number, direction: CardinalDirection) {
    // ...
}

move(1,"North"); // Okay
move(1,"Nurth"); // Error!