code: function checkExistsName(filePath, isDir, callback, count){ // callback(err, fullPath)
      if(typeof callback !== 'function') throw new Error('Wrong arguments');
      var pathInfo = resolve(filePath), newFullPath, oldName;
      count = count || 1;
      
      fs.exists(pathInfo.fullPath, function(exists){
          if(!exists) callback(null, pathInfo.fullPath);
          else { // generate new file or dir name, and try again
              oldName = count>1 ? '('+(count-1)+')' : '';
              if(isDir) {
                  newFullPath = pathInfo.fullPath.replace(new RegExp(oldName.escape()+'$'),'') + '(' +count+ ')';
              }
              else {
                  oldName = oldName + '.' + pathInfo.extName;
                  newFullPath = pathInfo.fullPath.replace(new RegExp(oldName.escape()+'$'), '(' +count+ ').' + pathInfo.extName);
              }
              checkExistsName(newFullPath, isDir, callback, count+1);
          }
      });
  }
docs: check if file or path already exists, and append number "_(1)"
  @param {String} filePath full path
  @param {Boolean} isDir
  @param {Function} callback
  @param {Number} count