createNode: function (fileInfo) {
      let nodeKey = fileInfo.rootDir
      if (nodeKey.charAt(nodeKey.length - 1) !== path.sep) {
        nodeKey += path.sep
      }
      if (fileInfo.fileName === path.sep) {
        fileInfo.fileName = nodeKey
      }
      else {
        nodeKey += fileInfo.fileName
      }
      // get file mime type
      const mimeType = mime.lookup(nodeKey)
      // create object
      return {
        label: fileInfo.fileName,
        nodeKey: nodeKey,
        expandable: fileInfo.isDir,
        tickable: true,
        lazy: true,
        children: [],
        data: {
          rootDir: fileInfo.rootDir,
          isDir: fileInfo.isDir,
          mimeType: mimeType,
          stat: fileInfo.stat
        }
      }
    },