Function hash

src/Hash.ts:5–48

(o: unknown)

const defaultValueOf = Object.prototype.valueOf;

export function hash(o: unknown): number {
  // eslint-disable-next-line eqeqeq
  if (o == null) {
    return hashNullish(o);
  }

  // @ts-expect-error don't care about object beeing typed as `{}` here
  if (typeof o.hashCode === 'function') {
    // Drop any high bits from accidentally long hash codes.
    // @ts-expect-error don't care about object beeing typed as `{}` here
    return smi(o.hashCode(o));
  }

  const v = valueOf(o);

  // eslint-disable-next-line eqeqeq
  if (v == null) {
    return hashNullish(v);
  }

  switch (typeof v) {
    case 'boolean':
      // The hash values for built-in constants are a 1 value for each 5-byte
      // shift region expect for the first, which encodes the value. This
      // reduces the odds of a hash collision for these common values.
      return v ? 0x42108421 : 0x42108420;
    case 'number':
      return hashNumber(v);
    case 'string':
      return v.length > STRING_HASH_CACHE_MIN_STRLEN
        ? cachedHashString(v)
        : hashString(v);
    case 'object':
    case 'function':
      return hashJSObj(v);
    case 'symbol':
      return hashSymbol(v);
    default:
      if (typeof v.toString === 'function') {
        return hashString(v.toString());
      }
      throw new Error('Value type ' + typeof v + ' cannot be hashed.');
  }
}

function hashNullish(nullish: null | undefined): number {
  return nullish === null ? 0x42108422 : /* undefined */ 0x42108423;