code: function maybeIdentifier(key) {
          var result = false,
              i;
  
          for (i = 0; i < key.length; i++) {
              result = Acorn.isIdentifierChar(key.charCodeAt(i));
              if (!result) {
                  break;
              }
          }
  
          return result;
      }
docs: Is the string key perhaps a valid JavaScript identifier?
  
  @param {string} key - string to test.
  @return {boolean} - could key be a valid identifier?