code: function listWebm (...args) {
    let board
    let threadNo
    let protocol
  
    if (args[1] === undefined) {
      ;({ board, threadNo, protocol } = parseUrl(args[0]))
    } else {
      [ board, threadNo ] = args
      args[2] = args[2] || {}
      protocol = args[2].https ? 'https' : 'http'
    }
  
    const apiUrl = `${protocol}://a.4cdn.org/${board}/thread/${threadNo}.json`
  
    return axios.get(apiUrl).then(res => transform(res.data, protocol, board))
  }
docs: Get webm data from a thread
  @func    listWebm
  @param   {Array} args      Argument array containing either a thread URL,
  or a board shortname and a thread number
  @returns {Promise<Object>} Resolves to JSON object with webm URLs