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My Favorite JavaScript Tips and Tricks

Tapas Adhikary on September 08, 2020

Motivation Most of the programming languages are open enough to allow programmers to do things multiple ways for a similar outcome. Java...

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Julio Betta • Sep 11 '20

hey, awesome article. just a small correction

let age = person.age ?? 35; // sets the value 35 if age is undefined, 0, null, '' etc

because of the null coalescing, if person.age === 0, the variable age is 0.

const person = {
  name: 'Adhikary',
  age: 0
};

const age1 = person.age ?? 35; // => 0
const age2 = person.age || 35; // => 35

Tapas Adhikary • Sep 11 '20

Big thank for helping me to correct the typo.

Elliot • Sep 11 '20

Hadn't seen the isRequired idea before! Clever list :)

Tapas Adhikary • Sep 12 '20

Thanks Elliot!

Nicolas Hervé • Sep 9 '20

Number.isInteger method was designed to be used with numbers in order to test if it is an integer or not (NaN, Infinity, float...).

Number.isInteger(12) // true
Number.isInteger(12.0) // true
Number.isInteger(12.5) // false

developer.mozilla.org/en-US/docs/W...
Using typeof mynum === "number" is a better solution to test if a value is a number.

typeof mynum // number
typeof mynumStr // string

Jan Küster • Sep 11 '20 • Edited

Note, that the Number rounding of floats in JavaScript is not accurate

(0.1 + 0.2) === 0.3 // false

Since this rounding affects integer representation, too, you should also consider Number.isSafeInteger

developer.mozilla.org/en-US/docs/W...

Also please consider Integer boundaries in JS, that are represented by Number.MAX_SAFE_INTEGER and Number.MIN_SAFE_INTEGER

developer.mozilla.org/en-US/docs/W...

Edit: sry wanted to post on top level, somehow ended up as comment on yours

Tapas Adhikary • Sep 11 '20

Awesome, thanks Jan!

Oscar Calderon • Sep 8 '20

I thought I would know everything in this list, but learned something new!!! Didn't know about the nullish coalescing operator, pretty useful! Thank you Tapas

Tapas Adhikary • Sep 8 '20

Thanks, Oscar!

marcellothearcane • Oct 12 '20

It's quite new, so it won't work everywhere yet.

rajmohan s • Nov 6 '20

?? operator not working for me. shows as below
SyntaxError: Unexpected token '?'

Tapas Adhikary • Nov 6 '20

Which browser are you using? It should work.

let person = {name: 'Jack'};
let age = person.age ?? 35; // sets the value 0 if age 0, 35 in case of undefined and null
console.log(`Age of ${person.name} is ${age}`);