function isIndex(value, length) {
	  length = length == null ? MAX_SAFE_INTEGER : length;
	  return !!length &&
	    (typeof value == 'number' || reIsUint.test(value)) &&
	    (value > -1 && value % 1 == 0 && value < length);
	}
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`.