The double tilde ~~ operator in Javascript

Adding to the list of useful obscure operators in Javascript, today will discuss the double tilde ~~ operator.

What it does is remove everything after the decimal point. Think of it as a way to round a number.

Let's see it in action:

console.log( ~~ 7.34) // 7
console.log( ~~ -11.40) // -11

The full formula is:

const doubleTilde = (x) => {
    if(x < 0) return Math.ceil(x);
    else return Math.floor(x)
}

It also works with strings:

console.log( ~~ "7.34") // 7
console.log( ~~ "-11.40") // -11

For example, this can be used when we generate a random number for a HSL color in Javascript:

const randColor = `hsl(${~~(360 * Math.random())}, 100%, 50%)`

// will output something like "hsl(123, 100%, 50%)" 
// or  "hsl(123, 100%, 50%)"

Under the hood what is happening is that we are applying the single tilde operator twice. So actually, there is no real double tilde operator 😆.

But, we do have a double asterisk ** operator in Javascript.

📖 50 Javascript, React and NextJs Projects

Learn by doing with this FREE ebook! Not sure what to build? Dive in with 50 projects with project briefs and wireframes! Choose from 8 project categories and get started right away.

📖 50 Javascript, React and NextJs Projects

Learn by doing with this FREE ebook! Not sure what to build? Dive in with 50 projects with project briefs and wireframes! Choose from 8 project categories and get started right away.


Leave a Reply

Your email address will not be published. Required fields are marked *

Home Screencasts Best of Newsletter Search X

📖 50 Javascript, React and NextJs Projects

Hi friend! Before you go, just wanted to let you know about the 50 Javascript, React and NextJs Projects FREE ebook.

One of the best ways to learn is by doing the work. Choose from 8 project categories and get started right away:

  • Business & Real-World
  • Games & Puzzles
  • Fun & Interesting
  • Tools & Libraries
  • Personal & Portfolio
  • Project Add-Ons
  • Productivity
  • Clones

Learn by doing with this FREE ebook! Not sure what to build? Dive in with 50 projects complete with project briefs and wireframes!

Keep building and level up! Get all projects as an ebook right to your inbox!

X