REACT COOL DIMENSIONS

A React hook that measure an element's size and handle responsive components with highly-performant way, using ResizeObserver. Try it you will 👍🏻 it!

❤️ it? ⭐️ it on GitHub or Tweet about it.

⚡️ Try yourself: https://react-cool-dimensions.netlify.app

Features

🚀 Measures element's size with highly-performant way, using ResizeObserver.
🎣 Easy to use, based on React hook.
🍰 Easy to handle responsive components, provides an alternative solution to the container queries problem.
📦 Supports border-box size measurement.
🎛 Super flexible API design to cover most cases for you.
🔩 Supports custom refs for some reasons.
📜 Supports TypeScript type definition.
🗄️ Server-side rendering compatibility.
🦠 Tiny size (~ 1KB gzipped). No external dependencies, aside for the react.

Requirement

To use react-cool-dimensions, you must use react@16.8.0 or greater which includes hooks.

Installation

This package is distributed via npm.

$ yarn add react-cool-dimensions
# or
$ npm install --save react-cool-dimensions

Usage

react-cool-dimensions has a flexible API design, it can cover simple to complex use cases for you. Here are some examples to show you how does it work.

⚠️ Most modern browsers support ResizeObserver natively. You can also use polyfill for full browser support.

Basic Use Case

To report the size of an element by the width and height states.

import useDimensions from "react-cool-dimensions";

const App = () => {
  const { ref, width, height, entry, unobserve, observe } = useDimensions({
    onResize: ({ width, height, entry, unobserve, observe }) => {
      // Triggered whenever the size of the target is changed
    },
  });

  return (
    <div ref={ref}>
      Hi! My width is {width}px and height is {height}px
    </div>
  );
};

Responsive Components

We have media queries but those are based on the browser viewport not individual elements. In some case, we'd like to style components based on the width of a containing element rather than the browser viewport. To meet this demand there's a proposal for container queries, but it still doesn't exist today...

No worries, react-cool-dimensions provides an alternative solution for us! We can activate the responsive mode by the breakpoints option. It's a width-based solution, once it's activated we can easily apply different styles to a component according to the currentBreakpoint state. The overall concept as below.

import useDimensions from "react-cool-dimensions";

const Card = () => {
  const { ref, currentBreakpoint } = useDimensions({
    // The "currentBreakpoint" will be the object key based on the target's width
    // for instance, 0px - 319px (currentBreakpoint = XS), 320px - 479px (currentBreakpoint = SM) and so on
    breakpoints: { XS: 0, SM: 320, MD: 480, LG: 640 },
    onResize: ({ currentBreakpoint }) => {
      // Now the event callback will be triggered when breakpoint is changed
      // we can also access the "currentBreakpoint" here
    },
  });

  return (
    <div class={`card ${currentBreakpoint}`} ref={ref}>
      <div class="card-header">I'm 😎</div>
      <div class="card-body">I'm 👕</div>
      <div class="card-footer">I'm 👟</div>
    </div>
  );
};

Note: If the breakpoints option isn't set or there's no the defined breakpoint (object key) for a range of width. The currentBreakpoint will be empty string;

Border-box Size Measurement

By default, the hook reports the width and height based on the content rectangle of the target element. We can include the padding and border for measuring by the useBorderBoxSize option. Please note, the width and height states are rely on the ResizeObserverEntry.borderBoxSize but it hasn't widely implemented by browsers therefore we need to use polyfill for this feature.

import useDimensions from "react-cool-dimensions";
import { ResizeObserver } from "@juggle/resize-observer";

const App = () => {
  const { ref, width, height } = useDimensions({
    useBorderBoxSize: true, // Tell the hook to measure based on the border-box size, default is false
    polyfill: ResizeObserver, // Use polyfill to make this feature works on more browsers
  });

  return (
    <div
      style={{
        width: "100px",
        height: "100px",
        padding: "10px",
        border: "5px solid grey",
      }}
      ref={ref}
    >
      {/* Now the width and height will be: 100px + 10px + 5px = 115px */}
      Hi! My width is {width}px and height is {height}px
    </div>
  );
};

Dynamic Component

There're two ways to use react-cool-dimensions with a dynamic show/hide component.

Option 1, we can lazily start observing via the observe method:

import { useState } from "react";
import useDimensions from "react-cool-dimensions";

const App = () => {
  const [show, setShow] = useState(false);
  const { width, height, observe } = useDimensions();

  return (
    <>
      <button onClick={() => setShow(!show)}>Toggle</button>
      {show && (
        <div
          ref={(el) => {
            if (el) observe(el);
          }}
        >
          Hi! My width is {width}px and height is {height}px
        </div>
      )}
    </>
  );
};

Option 2, wrap the hook into a component:

import { useState } from "react";
import useDimensions from "react-cool-dimensions";

const MyComponent = () => {
  const { ref, width, height } = useDimensions();

  return (
    <div ref={ref}>
      Hi! My width is {width}px and height is {height}px
    </div>
  );
};

const App = () => {
  const [show, setShow] = useState(false);

  return (
    <>
      <button onClick={() => setShow(!show)}>Toggle</button>
      {show && <MyComponent />}
    </>
  );
};

Use Your Own `ref`

In case of you had a ref already or you want to share a ref for other purposes. You can pass in the ref instead of using the one provided by this hook.

const ref = useRef();
const { width, height } = useDimensions({ ref });

Performance Optimization

The onResize event will be triggered whenever the size of the target element is changed. We can reduce the frequency of the event callback by activating the responsive mode or implementing our own throttled/debounced function as below.

import _ from "lodash";

const { ref, width, height } = useDimensions({
  onResize: _.throttle(() => {
    // Triggered once per every 500 milliseconds
  }, 500),
});

API

const returnObj = useDimensions(options?: object);

Return object

It's returned with the following properties.

Key	Type	Description
`ref`	object	Used to set the target element for measuring.
`width`	number	The width of the target element in pixel.
`height`	number	The height of the target element in pixel.
`currentBreakpoint`	string	Indicates the current breakpoint of the responsive components.
`entry`	object	The ResizeObserverEntry of the target element.
`unobserve`	function	To stop observing the target element.
`observe`	function	To lazily start or re-start observing the target element once it's stopped observing.

Parameter

The options provides the following configurations and event callback for you.

Key	Type	Default	Description
`ref`	object		For some reasons, you can pass in your own `ref` instead of using the built-in.
`breakpoints`	object		Activates the responsive mode for responsive components or performance optimization.
`useBorderBoxSize`	boolean	`false`	Tells the hook to measure the target element based on the border-box size.
`onResize`	function		It's invoked whenever the size of the target element is changed. But in responsive mode, it's invoked based on the changing of the breakpoint rather than the size.
`polyfill`	ResizeObserver		It's used for injecting a polyfill.

ResizeObserver Polyfill

ResizeObserver has good support amongst browsers, but it's not universal. You'll need to use polyfill for browsers that don't support it. Polyfills is something you should do consciously at the application level. Therefore react-cool-dimensions doesn't include it.

We recommend using @juggle/resize-observer:

$ yarn add @juggle/resize-observer
# or
$ npm install --save @juggle/resize-observer

Then inject it by the polyfill option:

import { ResizeObserver } from "@juggle/resize-observer";

const { width, height } = useDimensions(ref, { polyfill: ResizeObserver });

Or pollute the window object:

import { ResizeObserver, ResizeObserverEntry } from "@juggle/resize-observer";

if (!("ResizeObserver" in window)) {
  window.ResizeObserver = ResizeObserver;
  // Only use it when you have this trouble: https://github.com/wellyshen/react-cool-dimensions/issues/45
  // window.ResizeObserverEntry = ResizeObserverEntry;
}

You could use dynamic imports to only load the file when the polyfill is required:

(async () => {
  if (!("ResizeObserver" in window)) {
    const module = await import("@juggle/resize-observer");
    window.ResizeObserver = module.ResizeObserver;
    // Only use it when you have this trouble: https://github.com/wellyshen/react-cool-dimensions/issues/45
    // window.ResizeObserverEntry = module.ResizeObserverEntry;
  }
})();

Contributors ✨

Thanks goes to these wonderful people (emoji key):

_Welly

💻

📖

🚧

This project follows the all-contributors specification. Contributions of any kind welcome!

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