typed-array-constructor/index.js

Get a typed array constructor based on the hypothetical max value it could contain. Signed or unsigned.

/**
 * @module typedArrayConstructor
 */

const upperBounds = new Map();
upperBounds.set([Int8Array, Uint8Array], 255);
upperBounds.set([Int16Array, Uint16Array], 65535);
upperBounds.set([Int32Array, Uint32Array], 4294967295);
upperBounds.set([BigInt64Array, BigUint64Array], 2 ** 64 - 1);
const upperBoundsArray = Array.from(upperBounds.entries());

/**
 * Get a typed array constructor based on the hypothetical max value it could contain. Signed or unsigned.
 *
 * @alias module:typedArrayConstructor
 * @param {number} maxValue The max value expected.
 * @param {boolean} signed Get a signed or unsigned array.
 * @returns {(Uint8Array|Uint16Array|Uint32Array|BigInt64Array|Int8Array|Int16Array|Int32Array|BigInt64Array)}
 * @see [MDN TypedArray objects]{@link https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray#typedarray_objects}
 */
const typedArrayConstructor = (maxValue, signed) => {
  const value = signed ? Math.abs(maxValue) : Math.max(0, maxValue);
  return upperBoundsArray[
    upperBoundsArray.findLastIndex(
      ([_, bound]) =>
        value >
        Math[Math.sign(maxValue) === -1 ? "ceil" : "floor"](
          bound / (signed ? 2 : 1),
        ),
    ) + 1
  ][0][signed ? 0 : 1];
};

export default typedArrayConstructor;