View for Uint8Array emulating BooleanArray or BitSet

boolean_array_view.ts

// SPDX-License-Identifier: CC0-1.0
// Creative Commons Zero v1.0 Universal License: https://creativecommons.org/publicdomain/zero/1.0/deed

class BooleanArrayView {
  array: Uint8Array;

  constructor(array: Uint8Array) {
    this.array = array;

    return new Proxy(this, {
      get(target, prop) {
        return prop in target
          ? target[prop as keyof typeof target]
          : target.get(Number(prop));
      }
    });
  }

  get(index: number) {
    const chunkIndex = Math.floor(index / 8);
    const mask = 1 << (7 - (index % 8));
    return (this.array[chunkIndex] & mask) > 0;
  }
}

const data = new Uint8Array([128]); // 0b1000'0000
const view2 = new BooleanArrayView(data);
console.log(view2[0]); // true
console.log(view2.get(1)); // false