Handling complex condition without if statements with bitwise operators and bit masks

bitwise-config.test.ts

/*
+--------------------------------+---------------+
|              type              | bitmask       |
+--------------------------------+---------------+
| mode (light, dark)             | 0b0100        |
| screen size (xs, sm, md, lg)   | 0b0011        |
+--------------------------------+---------------+
*/

type Bits = number;

const BITMASK_MODE = 0b0100;
enum Mode {
  Light = 0b0000,
  Dark = 0b0100,
}

const BITMASK_SCREEN = 0b0011;
enum ScreenSize {
  XS = 0b0000,
  SM = 0b0001,
  MD = 0b0010,
  LG = 0b0011,
}

const actions = {
  [Mode.Light | ScreenSize.XS]: function () {
    return "Light / XS";
  },
  [Mode.Light | ScreenSize.SM]: function () {
    return "Light / SM";
  },
  [Mode.Light | ScreenSize.MD]: function () {
    return "Light / MD";
  },
  [Mode.Light | ScreenSize.LG]: function () {
    return "Light / LG";
  },
  [Mode.Dark | ScreenSize.XS]: function () {
    return "Dark / XS";
  },
  [Mode.Dark | ScreenSize.SM]: function () {
    return "Dark / SM";
  },
  [Mode.Dark | ScreenSize.MD]: function () {
    return "Dark / MD";
  },
  [Mode.Dark | ScreenSize.LG]: function () {
    return "Dark / LG";
  },
};

interface IConfig {
  mode: Mode;
  screenSize: ScreenSize;
}

test("Handling complex condition without if statements with bitwise operators and bit masks", () => {
  const config: IConfig = {
    mode: Mode.Dark,
    screenSize: ScreenSize.LG,
  };

  const bits = configToBits(config);
  expect(bits).toBe(0b111);
  expect(bits & BITMASK_MODE).toBe(0b100);
  expect(bits & BITMASK_MODE).toBe(Mode.Dark);
  expect(bits & BITMASK_SCREEN).toBe(0b011);
  expect(bits & BITMASK_SCREEN).toBe(ScreenSize.LG);
  expect(createScreen(config)).toBe("Dark / LG");
});

function configToBits(config: IConfig): Bits {
  let bits = 0b0;

  for (const key in config) {
    if (config.hasOwnProperty(key)) {
      bits |= (config as any)[key];
    }
  }

  return bits;
}

function createScreen(config: IConfig) {
  return actions[configToBits(config)]?.();
}