code: function isIndex(value, length) {
    var type = typeof value;
    length = length == null ? MAX_SAFE_INTEGER$1 : length;
  
    return !!length &&
      (type == 'number' ||
        (type != 'symbol' && reIsUint.test(value))) &&
          (value > -1 && value % 1 == 0 && value < length);
  }
docs: Checks if `value` is a valid array-like index.
  
  @private
  @param {*} value The value to check.
  @param {number} [length=MAX_SAFE_INTEGER] The upper bounds of a valid index.
  @returns {boolean} Returns `true` if `value` is a valid index, else `false`.