Express & Node JS Cheat Sheet

Some snippets to help you through common scenarios

Express

Modules with Named Exports

If you have a file:

database.js

export const getData = () => {
  ...
}

• export is a keyword to say that this variable can be accessed from another file

Then you can import that file this way:

app.js

import { getData } from './database.js'

getData()

OR

app.js

import * as database from './database.js'
database.getData()

Modules with Default Exports

If you have a file

database.js

const getData = () => {
  ...
}
export default getData;

• export default is a keyword to say that the variable/object will be exported by default from this file
• You can only have 1

Then you can import it:

app.js

import getData from './database'

getData()

generateRandomNumber

Generates random 6-digit number

const generateRandomNumber = () => {
  return Math.floor(100000 + Math.random() * 900000)
}

Array.find

Given this array

const chatrooms = [{
  name: "channel-1"
}, {
  name: "channel-2"
}]

Find an element, given a condition defined as a function. Will return the 1st item it finds, or undefined if it can't find anything

const chatroom = chatrooms.find(chatroom => chatroom.name === 'channel-1')
if (chatroom) {
  console.log('found the chatroom!')
} else {
  console.log('No chatroom found')
}

Array.filter

Given this data:

const chatrooms = [{
  name: "channel-1",
  members: []
}, {
  name: "channel-2",
  members: ["danny"]
}]

Returns all elements that match a condition defined as a function. Will return a new array with all matching items.

const chatroomsWithMembers = chatrooms.filter(chatroom => chatroom.members.length > 0)
if (chatroomsWithMembers.length === 0) {
  console.log('No chatrooms found')
} else {
  console.log('Found chatrooms with members', chatroomsWithMembers)
}