react-slidedown

React component which uses CSS to animate a child from its current height to height: auto when mounting/updating/unmounting.

Live Demo

Overview

CSS does not currently support animating element height to height: auto and so normally javascript is used to achieve this effect.

This component uses CSS to perform the animation, following an algorithm (first described here). The desired height of the element is calculated, and then css is used to transition that height. After the transition has completed the height is set to height: auto.

react-slidedown is perfect for dropdown lists, popup menus, accordions and closeable panels which have varying sized content.

I am not aware of any cross-browser issues from IE10 and onwards.

Installation

npm install react-slidedown --save

Usage

Simply wrap the component you want to slide with the SlideDown component:

import React from 'react'

import {SlideDown} from 'react-slidedown'
import 'react-slidedown/lib/slidedown.css'

export function MyDropdown(props) {
  return (
    <SlideDown className={'my-dropdown-slidedown'}>
      {props.open ? props.children : null}
    </SlideDown>
  )
}

In the example above the css file needed by react-slidedown is included via JavaScript which is the normal way of doing things when using webpack css-loader, it is also populated in the style property of package.json so if you are using parcelify it should get included automatically. Otherwise it is also possibe to import it from css:

@import "node_modules/react-slidedown/lib/slidedown.css";

Props

Property	Type	Default	Required?	Description
as	String	div	No	The outermost Element type to render
children	Children		No	When provided the component opens and when removed the component closes
className	String	react-slidedown	No	CSS class name to be used on the element
closed	Boolean		No	If true the component will close even if children are provided
closedClassName	String	closed	No	CSS class name to be used on the element when closed
transitioningClassName	String	transitioning	No	CSS class name to be used on the element while in transition
transitionOnAppear	Boolean	true	No	Do a transition animation on initial mount

Example

To quickly see a live demonstration of react-slidedown go here.

To build and run this example project:

git clone https://github.com/frankwallis/react-slidedown.git
cd react-slidedown
npm install
npm start

Customisation

You can customise the transition used for the animation by overriding styles on the SlideDown component:

.react-slidedown.my-dropdown-slidedown {
    transition-duration: 1.2s;
    transition-timing-function: cubic-bezier(0.1, 0.7, 1.0, 0.1);
}

The default values used are:

.react-slidedown {
    transition-duration: .5s;
    transition-timing-function: ease-in-out;
}