TypeScript: add more data to enum

Unfortunately it's not possible. You can just assign property names

See this reference for the TypeScript spec https://github.com/microsoft/TypeScript/blob/30cb20434a6b117e007a4959b2a7c16489f86069/doc/spec-ARCHIVED.md#a7-enums

Not using an enum, but you can get the same exact thing using a class and a few static members:

class Planet {
    public static MERCURY = new Planet(3.303e+23, 2.4397e6);
    public static VENUS = new Planet(4.869e+24, 6.0518e6);
    public static EARTH = new Planet(5.976e+24, 6.37814e6);
    public static MARS = new Planet(6.421e+23, 3.3972e6);
    public static JUPITER = new Planet(1.9e+27, 7.1492e7);
    public static SATURN = new Planet(5.688e+26, 6.0268e7);
    public static URANUS = new Planet(8.686e+25, 2.5559e7);
    public static NEPTUNE = new Planet(1.024e+26, 2.4746e7);

    private mass: number;
    private radius: number;

    private constructor(mass: number, radius: number) {
        this.mass = mass;
        this.radius = radius;
    }

    public static G = 6.67300E-11;

    public surfaceGravity(): number {
        return Planet.G * this.mass / (this.radius * this.radius);
    }

    public surfaceWeight(otherMass: number) {
        return otherMass * this.surfaceGravity();
    }
}

console.log(Planet.MERCURY.surfaceGravity());

(code in playground)

In java for each item in the enum a static instance is created, which means that this indeed does the same thing, it's just that java has a nicer syntax for defining enums.

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Edit

Here's a version with the equivalent Planet.values() which java will generate:

class Planet {
    public static MERCURY = new Planet(3.303e+23, 2.4397e6);
    public static VENUS = new Planet(4.869e+24, 6.0518e6);
    ...

    private static VALUES: Planet[] = [];

    private mass: number;
    private radius: number;

    private constructor(mass: number, radius: number) {
        this.mass = mass;
        this.radius = radius;

        Planet.VALUES.push(this);
    }

    public static values() {
        return Planet.VALUES;
    }

    ...
}

---

2nd edit

Here's a way to implement the valueOf:

   public static valueOf(name: string): Planet | null {
        const names = Object.keys(this);
        for (let i = 0; i < names.length; i++) {
            if (this[names[i]] instanceof Planet && name.toLowerCase() === names[i].toLowerCase()) {
                return this[names[i]];
            }
        }

        return null;
    }