Function wrapIndex

src/TrieUtils.ts:43–62

(
  iter: Collection<unknown, unknown>,
  index: number
)

}

export function wrapIndex(
  iter: Collection<unknown, unknown>,
  index: number
): number {
  // This implements "is array index" which the ECMAString spec defines as:
  //
  //     A String property name P is an array index if and only if
  //     ToString(ToUint32(P)) is equal to P and ToUint32(P) is not equal
  //     to 2^32−1.
  //
  // http://www.ecma-international.org/ecma-262/6.0/#sec-array-exotic-objects
  if (typeof index !== 'number') {
    const uint32Index = index >>> 0; // N >>> 0 is shorthand for ToUint32
    if ('' + uint32Index !== index || uint32Index === 4294967295) {
      return NaN;
    }
    index = uint32Index;
  }
  return index < 0 ? ensureSize(iter) + index : index;
}

export function returnTrue(): true {
  return true;