JavaScript Code Style
Coder100 (12455)

JavaScript, unlike many languages, has a very diverse code style. This is probably a combination of not only ASI (Automatic Semicolon Insertion) code style, but also if quotes should be used or not, and type safety.

So without further ado, lets talk about my favorite code style!

Coder100's code style


Semicolons are always required, but beware of ASI.

console.log("hey :smirk:"); // <-- good!
console.log("hey :smirk:") // <-- avoid!


ASI automatically inserts a semicolon if the program errors. You can read up here


Due to how often we're using single quotes, it is very recommended to use double quotes. Also in lower level languages, double quotes signify a string, and I believe it is wise to adapt that into your coding as well.

console.log("Let's go outside!");  // <-- good!
console.log('Let\'s go outside!') // <-- avoid!

However, the exception is when you require double quotes:

console.log("\"That's what she said\""); // <-- avoid!
console.log('"I am Coder100"'); // <-- good!
console.log('"That\'s what she said"'); // <-- edge case
console.log(`"That's what she said"`); // <-- good!

Try to minimize escaping, and if there is no need for escaping, just use ".


I have always used two spaces, but sometimes I use 4, and sometimes I use tabs. So which one should we use? I flipped a coin between two spaces and tabs and got two spaces, so that's what we are using.

function hi() {
  return 5; // <-- good!

function hi() {
	return 5; // <-- avoid!

Resolving Paths

Use path.join, not only is it going to make your life easier, it also allows you to make more complex paths.

const path = require("path");

path.join(__dirname, "./index.html"); // <-- good!
__dirname + "/index.html"; // <-- avoid!


I haven't found much use for destructuring, but just make sure you add spaces:

const {log} = console; // <-- avoid!
const { log } = console; // <-- good!
const { log, debug, dir, table, error, warn } = console; // <-- good!
const { log,
        warn } = console; // <-- consider using no wrap (avoid)


This code snippet will tell you everything.

if (true) {
  // this is what we want
} else {
  console.log("POG UR COMPUTER IS BROKE");

function poggers(a) {
  return 5;

let myArr = [1, 2, 3];


Arrow functions

I only use arrow functions as lambdas. You should too. It allows you to define functions anywhere!

const bad = () => console.log("bad"); // <-- avoid!


function hi() { // <-- good!

[1, 2, 3].map(n => n ** 2); // <-- good!
[1, 2, 3].map(function square(n) {
  return n ** 2;
}); // <-- uh ew (avoid)

Also anonymous functions should always be converted to arrow functions, except for when binding.

const x = {
  key: "value",
  func: () => this.key // good!
x.func(); // => undefined

const y = {
  key: "value",
  func: function () { return this.key; } // good!
y.func(); // => "value"

Function Definition

I normally call functions before defining them,


function a() {

however, what you want is really up to you. However, never define functions within loops.

for (let i = 0; i < 10; i++) {
  function a() { return i; }


Like rust, make sure to define everything as constant. Only when you need to change mutability should you change the const keyword to let.

const a = 5; // <-- good!
const b = 10; // <-- good!
let g = 10; // <-- good!

let j = 3; // <-- avoid!

Objects and Arrays

These can be prefixed with let if you are going to change them. const isn't only for the interpreter, it is also for programmers.

const a = {
  b: 6

a.b = 6; // <-- avoid!

If you want objects to be constant, consider also adding Object.freeze()

const a = Object.freeze({
  b: 6

a.b = 10; // <-- will silently fail

Same goes with arrays.

Member Access

The final code style is with member access. Try to use . as much as you can, but use [] for variables and numbers.

let a = { b: 6 };
a.b = 10; // <-- good!
a[3] = 10; // <-- good!
a["b"] = 10; // <-- bad!


Hopefully you like this code style. Finally I have peaked in good coding practices!
In the next tutorial, I will be showing you how to use eslint to enforce this code style :))

See you then!


Special thanks to @fuzzyastrocat and @Baconman321 for pointing out some edge cases

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firefish (879)

@Coder100 Why you always use arrow functions:
The function keyword hoists, so don't use that unless in conjunction with let or use strict;,
and scoping is mucked up in functions. Normal function use this in the scope of the caller, however arrow functions use this in the scope of the callee, a.k.a the sane way.

fuzzyastrocat (1463)

@firefish I don't think it's always 100% sane though. I mean, put yourself in the shoes of a newbie JS programmer. What do you expect this to return:

const x = {
  prop: 1,
  func: () => this.prop

It seems like that should return 1, but no, it returns undefined since there's no global prop. However using a function() { return this.prop; } will return 1 as expected, so I would argue that sometimes arrow functions can be more confusing.