Guidelines

General

Indentation

Soft: 2 Spaces

Line break

UNIX like: LF

Encoding

UTF-8

EOF

Always end with a Blank Line

Semicolons

Nope

References

Use const for all of your references; avoid using var.

Why? This ensures that you can’t reassign your references, which can lead to bugs and difficult to comprehend code.

// bad
var a = 1

// good
const a = 1

If you must reassign references, use let instead of var.

Why? let is block-scoped rather than function-scoped like var.

// bad
var count = 1
if (true) {
  count += 1
}

// good, use the let.
let count = 1
if (true) {
  count += 1
}

Declarative and Functional

The code should simply describe how it does and not what it uses to do it.

// bad
const greetUser = userId => {
  const user = getUser(userId)
  return 'Hello ${user.name}'
}

// good
const greet = name => `Hello ${name}`
const greetUser = flow(
  getUser,
  greet,
)

// bad
const deleteFileMentions = async channelId => {
  const messages = await getHistory({ channelId })
  const fileMentions = filter(flow(get('subtype'), eq('file_share')))(messages)
  return map(({ ts }) =>
    deleteMessage({ ts, channelId }))(fileMentions))
}

// good
const isFileShare = m => m.subtype === 'file_share'

const deleteFileMentions = async channelId => {
  const deleteFileMessages = flow(
    filter(isFileShare),
    map(({ ts }) => deleteMessage({ channel: channelId, ts })),
  )
  return getHistory({ channelId })
    .then(deleteFileMessages)
}

One thought per line.

Keep to one call or assignment per line.

Why? It is easy to understand and read through the code.

// bad
const a = `Hello ${await getWorld()}`
const b = get('name')(await fetchArray())

// good
const world = await getWorld()
const a = `Hello ${world}`
const b =
  await fetchArray()
    .then(get('name'))

Write self-documenting code, avoid using comments

We're writing code for humans, if we wanted to write for machines we would be using C. Functions should have name compatible with their arguments and with what they do.

Why? If the code is not explicitly telling what it does, a comment won't help.

// bad
/**
 * Deletes message from a channel.
 * @param {string} id - ID of the channel
 * @param {string} ts - Timestamp of the message
 */
const delete = (id, ts) => slack.chat.delete({ channel: id, ts })

// good
const deleteMessageFromChannel => (channel, message) =>
  slack.chat.delete({ channel: channel.id, ts: message.ts })