code: private JSType getNativeTypeForTypeOf(String value) {
      switch (value) {
        case "number":
          return getNativeType(NUMBER_TYPE);
        case "boolean":
          return getNativeType(BOOLEAN_TYPE);
        case "string":
          return getNativeType(STRING_TYPE);
        case "symbol":
          return getNativeType(SYMBOL_TYPE);
        case "undefined":
          return getNativeType(VOID_TYPE);
        case "function":
          return getNativeType(U2U_CONSTRUCTOR_TYPE);
        default:
          return null;
      }
    }
docs: If we definitely know what a type is based on the typeof result,
  return it.  Otherwise, return null.
  
  The typeof operation in JS is poorly defined, and this function works
  for both the native typeof and goog.typeOf. It should not be made public,
  because its semantics are informally defined, and would be wrong in
  the general case.