code: function isJsonFile (file) {
    return file.data &&                             // The file has data
      (typeof file.data === 'string') &&            // and it's a string
      (
        mimeTypePattern.test(file.mimeType) ||      // and it has a JSON MIME type
        extensionPattern.test(file.url)             // or at least a .json file extension
      );
  }
docs: Determines whether the file data is JSON
  
  @param {File} file
  @returns {boolean}