Skip to content
Swizec Teller - a geek with a hatswizec.com

useDimensions – a React Hook to measure DOM nodes

Yes it's new, I just open sourced it 😛

The other day I wanted to measure some DOM nodes. This is useful when you have to align items, or respond to browser width, or ... lots of reasons okay.

I had to align a curvy line with elements that aren't under my control. This little stepper component uses flexbox to evenly space circles, CSS layouting aligns the title, and you see where this is going.

SVG in the background detects position of itself, positions of the title and circle, and uses those to define the start and end line of my curve. 👌

Many ways you can do this.

@lavrton linked to a list of existing NPM packages that sort of do it. @mcalus shared how he uses react-sizeme to get it done.

All great, but I wanted something even simpler. I also didn't know about them and kind of just wanted to make my own.

Here's an approach I found works great

useDimensions hook

This seemed like a neat approach so I turned it into an open source React Hook. You might enjoy it.

useDimensions source
useDimensions source

useDimensions source

Yep that's it. It really is that simple.

👉 GitHub link

  • useRef creates a React.ref, lets you access the DOM
  • useState gives you place to store/read the result
  • useLayoutEffect runs before browser paint but after all is known
  • getClientBoundingRect() measures a DOM node. Width, height, x, y, etc
  • toJSON turns a DOMRect object into a plain object so you can destructure

Here's how to use it in your project 👇

First, add useDimensions to your project

$ yarn add react-use-dimensions
or
$ npm install --save react-use-dimensions

Using it in a component looks like this

<code class="javascript">import React from 'react';
import useDimensions from 'react-use-dimensions';
const MyComponent = () => {
    const [ref, { x, y, width }] = useDimensions();
    return (
        <div ref={ref}>
            This is the element you'll measure
        </div>
    )
}

useDimensions returns a 2-element array. First the ref, second the dimensions.

This is so multiple useDimensions hooks in the same component don't step on each others' toes. Create as many refs and measurement objects as you'd like.

<code class="javascript">const MyComponent = () => {
    const [stepRef, stepSize] = useDimensions();
    const [titleRef, titleSize] = useDimensions();
    console.log("Step is at X: ", stepSize.x);
    console.log("Title is", titleSize.width, "wide");
    return (
        <div>
            <div ref={stepRef}>This is a step</div>
            <h1 ref={titleRef}>The title</h1>
        </div>
    )
}

MIT License of course.

Consider retweeting if you think it's neat

Enjoy ✌️ ~Swizec

Did you enjoy this article?

Published on March 13th, 2019 in Front End, Technical

Learned something new?
Want to become a high value JavaScript expert?

Here's how it works 👇

Leave your email and I'll send you an Interactive Modern JavaScript Cheatsheet 📖right away. After that you'll get thoughtfully written emails every week about React, JavaScript, and your career. Lessons learned over my 20 years in the industry working with companies ranging from tiny startups to Fortune5 behemoths.

Start with an interactive cheatsheet 📖

Then get thoughtful letters 💌 on mindsets, tactics, and technical skills for your career.

"Man, love your simple writing! Yours is the only email I open from marketers and only blog that I give a fuck to read & scroll till the end. And wow always take away lessons with me. Inspiring! And very relatable. 👌"

~ Ashish Kumar

Join over 10,000 engineers just like you already improving their JS careers with my letters, workshops, courses, and talks. ✌️

Have a burning question that you think I can answer? I don't have all of the answers, but I have some! Hit me up on twitter or book a 30min ama for in-depth help.

Ready to Stop copy pasting D3 examples and create data visualizations of your own?  Learn how to build scalable dataviz components your whole team can understand with React for Data Visualization

Curious about Serverless and the modern backend? Check out Serverless Handbook, modern backend for the frontend engineer.

Ready to learn how it all fits together and build a modern webapp from scratch? Learn how to launch a webapp and make your first 💰 on the side with ServerlessReact.Dev

Want to brush up on your modern JavaScript syntax? Check out my interactive cheatsheet: es6cheatsheet.com

By the way, just in case no one has told you it yet today: I love and appreciate you for who you are ❤️

Created bySwizecwith ❤️swizec.com
BlogBooksCoursesWorkshopsAbout