Enum flags in JavaScript

Question

I need to emulate enum type in Javascript and approach seems pretty straight forward:

var MyEnum = {Left = 1; Right = 2; Top = 4; Bottom = 8}

N

Answer 1

There is my implementation in typescript:

export class FlagEnumService {

    constructor(private value: number = 0) {
    }

    public get() {
        return this.value;
    }

    public set(value: number): this {
        this.value = value;
        return this;
    }

    public has(key: number): boolean {
        return !!(this.value & key);
    }

    public add(key: number): this {
        this.value |= key;
        return this;
    }

    public delete(key: number): this {
        this.value &= ~key;
        return this;
    }

    public toggle(key: number): this {
        this.has(key) ? this.delete(key) : this.add(key);
        return this;
    }
}

And tests for clarification

import { FlagEnumService } from './flag-enum.service';

enum Test {
    None = 0,
    First = 1,
    Second = 2,
    Third = 4,
    Four = 8
}

describe('FlagEnumService', () => {
    let service: FlagEnumService;
    beforeEach(() => service = new FlagEnumService());

    it('should create with initial value', () => {
        service = new FlagEnumService(Test.First);
        expect(service.get()).toBe(Test.First);
    });

    it('should return true if has flag', () => {
        service = new FlagEnumService(Test.First);
        expect(service.has(Test.First)).toBe(true);
    });

    it('should return false if doesn\'t have flag', () => {
        service = new FlagEnumService(Test.First);
        expect(service.has(Test.Second)).toBe(false);
    });

    it('should add', () => {
        expect(service.add(Test.First).add(Test.Second).get()).toBe(Test.First + Test.Second);
    });

    it('should not add the same value twice', () => {
        expect(service.add(Test.First).add(Test.First).get()).toBe(Test.First);
    });

    it('should remove', () => {
        expect(
            service
                .add(Test.First)
                .add(Test.Second)
                .delete(Test.Second)
                .get()
        )
            .toBe(Test.First);
    });

    it('should return 0 when add then remove the same value', () => {
        expect(service.add(Test.First).delete(Test.First).get()).toBe(0);
    });

    it('should not remove not added values', () => {
        expect(service.add(Test.First).delete(Test.Second).get()).toBe(Test.First);
    });
});