Enumify with fromOrdinal

A JavaScript library for enums. To be used by transpiled ES6 (e.g. via Babel).

The approach taken by Enumify is heavily inspired by Java enums.

The basics

Install:

npm install enumify

Use:

import {Enum} from 'enumify-fork';

class Color extends Enum {}
Color.initEnum(['RED', 'GREEN', 'BLUE']);

console.log(Color.RED); // Color.RED
console.log(Color.GREEN instanceof Color); // true

new Color();
    // Error: Enum classes can’t be instantiated

Properties of enum classes

Enums get a static property enumValues, which contains an Array with all enum values:

for (const c of Color.enumValues) {
    console.log(c);
}
// Output:
// Color.RED
// Color.GREEN
// Color.BLUE

The inherited tool method enumValueOf() maps names to values:

console.log(Color.enumValueOf('RED') === Color.RED); // true
true

The inherited tool method fromOrdinal() maps value to name:

console.log(Color.fromOrdinal(0) === Color.RED); // true
true

Properties of enum values

Enumify adds two properties to every enum value:

• name: the name of the enum value.

  > Color.BLUE.name
  'BLUE'

• ordinal: the number representation.

  > Color.BLUE.ordinal
  2

Adding properties to enum values

initEnum() also accepts an object as its parameter. That enables you to add properties to enum values:

class TicTacToeColor extends Enum {}

// Alas, data properties don’t work, because the enum
// values (TicTacToeColor.X etc.) don’t exist when
// the object literals are evaluated.
TicTacToeColor.initEnum({
    O: {
        get inverse() { return TicTacToeColor.X },
    },
    X: {
        get inverse() { return TicTacToeColor.O },
    },
});

console.log(TicTacToeColor.O.inverse); // TicTacToeColor.X

Custom number representation

class Bytes extends Enum {
}
Bytes.initEnum({
    Byte: 1,
    KiloByte: 1024,
    MegaByte: 1024 * 1024,
});
console.log(Bytes.fromOrdinal(1024).name); // "KiloByte"

console.log(Number(Bytes.MegaByte)); // 1048576

More information

• The directory test/ contains examples.