code: function jstransform (file) {
    let commentblock
    var requires = []
    const stream = through()
    readline.createInterface({
      input: stream
    }).on('line', (line) => {
      if (relevant(line)) {
        if (!commentblock) {
          if (commentstart(line)) {
            if (!commentend(line)) {
              commentblock = true
            }
          } else if (hasrequire(line)) {
            var req
            while(req = required(line)) {
              if (!isBuiltinModule(req.uri)) {
                requires.push(req)
              }
            }
          }
        } else if (commentend(line)) {
          commentblock = false
        }
      }
    }).on('close', () => collect(requires, file))
    return stream
  }
docs: js transform