code: function parseObjectPropertyKey() {
    var token;
  
    index = lookahead.start;
    token = lex();
  
    // Note: This function is called only from parseObjectProperty(), where
    // EOF and Punctuator tokens are already filtered out.
  
    if (token.type === TokenStringLiteral || token.type === TokenNumericLiteral) {
      if (token.octal) {
        throwError(token, MessageStrictOctalLiteral);
      }
      return finishLiteral(token);
    }
  
    return finishIdentifier(token.value);
  }
docs: 11.1.5 Object Initialiser