code: function parseObjectPropertyKey() {
          var token;
  
          skipWhitespace();
          token = lex();
  
          // Note: This function is called only from parseObjectProperty(), where
          // EOF and Punctuator tokens are already filtered out.
          if (token.type === Token.StringLiteral || token.type === Token.NumericLiteral) {
              return delegate.createLiteral(token);
          }
  
          return delegate.createIdentifier(token.value);
      }
docs: 11.1.5 Object Initialiser