code: function(line) {
          //^
          // (\s*)        $1 opts leading spaces
          // ([\w$]+\s*)  $2 variable name & trailing spaces
          // (\=)         $3 division equals OR
          // \s*          opt spaces
          // (.*?)        rest of expression to assign
          // $
          var parts = line.match(/^(\s*)([\w$]+)\s*(\=)\s*(.*?)$/);
          if (!parts) return line;
  
          var leadingSpace = parts[1];
          var name = parts[2].trim();
          var operator = parts[3].trim();
          var rest = parts[4];
  
          return leadingSpace + 'const ' + name + ' ' + operator + ' ' + rest;
      }
docs: adds `const` to any declaration, works with shorthand operators String a -> String b