Lightweight React component for animating height using CSS transitions. Slide up/down the element, and animate it to any specific height. Content's opacity can be optionally animated as well (check animateOpacity prop bellow).

CSS classes are applied in specific animation states, check animationStateClasses prop.

Changelog

For React >=16.3.0 (17 included) make sure you are using v2.x.

Read more about React lifecycle changes introduced with React 16.3.

Live demo: muffinman.io/react-animate-height

Because multiple people asked how to animate list items, I created this simple example for that as well.

To build the examples locally, run:

npm install
npm start

Then open localhost:8080 in your browser of choice browser.

Or play with this sandbox.

Get it from npm

$ npm install --save react-animate-height

Import and use it in your React app.

import React, { Component } from 'react';
import AnimateHeight from 'react-animate-height';

export default class Example extends Component {
  state = {
    height: 0,
  };

  toggle = () => {
    const { height } = this.state;

    this.setState({
      height: height === 0 ? 'auto' : 0,
    });
  };

  render() {
    const { height } = this.state;

    return (
      <div>
        <button 
          aria-expanded={ height !== 0 }
          aria-controls='example-panel'
          onClick={ this.toggle }
        >
          { height === 0 ? 'Open' : 'Close' }
        </button>

        <AnimateHeight
          id='example-panel'
          duration={ 500 }
          height={ height } // see props documentation below
        >
          <h1>Your content goes here</h1>
          <p>Put as many React or HTML components here.</p>
        </AnimateHeight>
      </div>
    );
  }
}

• height: numeric or percentage value (ie. '50%') or 'auto', required

  When changed, element height will be animated to that height.
  To slide up use 0, for slide down use 'auto'

• duration: integer, default: 250

  Duration of the animation in milliseconds

• delay: integer, default: 0

  Animation delay in milliseconds

• easing: string, default: 'ease'

  CSS easing function to be applied to the animation

• id: string

  HTML id attribute.

• className: string

  CSS class to be applied to the element

  Please note that you shouldn't apply properties that are messing with the layout (like display, height...), as these might break height calculations

• style: object

  CSS style object, it will be merged with inline styles of the component

  Please note that you shouldn't apply properties that are messing with the layout (like display, height...), as these might break height calculations

• contentClassName: string

  CSS class to be applied to content wrapper element

  Please note that you shouldn't apply properties that are messing with the layout (like display, height...), as these might break height calculations

• animationStateClasses: object

  Object containing CSS class names for animation states, default:

  {
    animating:                  'rah-animating',
    animatingUp:                'rah-animating--up',
    animatingDown:              'rah-animating--down',
    static:                     'rah-static',
    animatingToHeightZero:      'rah-animating--to-height-zero',
    animatingToHeightAuto:      'rah-animating--to-height-auto',
    animatingToHeightSpecific:  'rah-animating--to-height-specific',
    staticHeightZero:           'rah-static--height-zero',
    staticHeightAuto:           'rah-static--height-auto',
    staticHeightSpecific:       'rah-static--height-specific',
  }
  

  Please note that this one will be merged with the default object and cached when component is created, so changing it afterwards will have no effect.

• onAnimationStart: function

  Callback which will be called when animation starts.

  This first argument passed to this callback is an object containing newHeight, the pixel value of the height at which the animation will end.

• onAnimationEnd: function

  Callback which will be called when animation ends.

  This first argument passed to this callback is an object containing newHeight, the pixel value of the height at which the animation ended.

• applyInlineTransitions: boolean, default: true

  If this flag is set to false only CSS classes will be applied to the element and inline transition styles will not be present.

• animateOpacity: boolean, default: false

  If set to true content will fade-in (and fade-out) while height is animated.

• aria-hidden: boolean

  By default, library will set aria-hidden to true when height is zero. If you wish to override it, you can pass the prop yourself.

Additional props will be passed to the wrapper div, to make adding attrs like aria-* easier.

Library will hide the content using display: hidden when height props is 0. It will also apply aria-hidden="true" in the same case, but you can override it by passing aria-hidden prop yourself.

When using a button to toggle height, make sure you add aria-expanded and aria-controls to make everything accessible. Here's an example:

<button 
  aria-expanded={ height !== 0 }
  aria-controls='example-panel' // it has to match the id passed to AnimateHeight
  onClick={ toggleHeight } // your click handler that toggles height
  // ... all other props
>
  Toggle
</button>

<AnimateHeight id='example-panel'>
  Content
</AnimateHeight>

If AnimateHeight is a flex child and it's parent has a fixed height, animation won't work. To fix this, you just need to add the following CSS rule to the AnimateHeight instance.

flex-shrink: 0;

You can do it by passing a className or directly in the style prop

<AnimateHeight style={{flexShrink: 0}}>

Check the issue #89 for the example and more details.

MIT