/downshift

🏎 Primitives to build simple, flexible, WAI-ARIA compliant enhanced input React components

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downshift 🏎
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Primitives to build simple, flexible, WAI-ARIA compliant React autocomplete/dropdown/select/combobox components

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The problem

You need an autocomplete/dropdown/select experience in your application and you want it to be accessible. You also want it to be simple and flexible to account for your use cases.

This solution

This is a component that controls user interactions and state for you so you can create autocomplete/dropdown/select/etc. components. It uses a render function as children which gives you maximum flexibility with a minimal API because you are responsible for the rendering of everything and you simply apply props to what you're rendering.

This differs from other solutions which render things for their use case and then expose many options to allow for extensibility resulting in a bigger API that is less flexible as well as making the implementation more complicated and harder to contribute to.

NOTE: The original use case of this component is autocomplete, however the API is powerful and flexible enough to build things like dropdowns as well.

Table of Contents

Installation

This module is distributed via npm which is bundled with node and should be installed as one of your project's dependencies:

npm install --save downshift

This package also depends on react and prop-types. Please make sure you have those installed as well.

Note also this library supports preact out of the box. If you are using preact then look in the dist/ folder and use the module you want with the preact suffix.

Usage

import Downshift from 'downshift'

function BasicAutocomplete({items, onChange}) {
  return (
    <Downshift onChange={onChange}>
      {({
        getInputProps,
        getItemProps,
        isOpen,
        inputValue,
        selectedItem,
        highlightedIndex
      }) => (
        <div>
          <input {...getInputProps({placeholder: 'Favorite color ?'})} />
          {isOpen ? (
            <div style={{border: '1px solid #ccc'}}>
              {items
                .filter(
                  i =>
                    !inputValue ||
                    i.toLowerCase().includes(inputValue.toLowerCase()),
                )
                .map((item, index) => (
                  <div
                    {...getItemProps({item})}
                    key={item}
                    style={{
                      backgroundColor:
                        highlightedIndex === index ? 'gray' : 'white',
                      fontWeight: selectedItem === item ? 'bold' : 'normal',
                    }}
                  >
                    {item}
                  </div>
                ))}
            </div>
          ) : null}
        </div>
      )}
    </Downshift>
  )
}

function App() {
  return (
    <BasicAutocomplete
      items={['apple', 'orange', 'carrot']}
      onChange={selectedItem => console.log(selectedItem)}
    />
  )
}

downshift is the only component. It doesn't render anything itself, it just calls the child function and renders that. Wrap everything in <Downshift>{/* your function here! */}</Downshift>.

Props

defaultSelectedItem

any | defaults to null

Pass an item or an array of items that should be selected by default.

defaultHighlightedIndex

number/null | defaults to null

This is the initial index to highlight when the menu first opens.

defaultInputValue

string | defaults to ''

This is the initial input value.

defaultIsOpen

boolean | defaults to false

This is the initial isOpen value.

itemToString

function(item: any) | defaults to: i => (i == null ? '' : String(i))

Used to determine the string value for the selected item (which is used to compute the inputValue.

getA11yStatusMessage

function({/* see below */}) | default messages provided in English

This function is passed as props to a Status component nested within and allows you to create your own assertive ARIA statuses.

A default getA11yStatusMessage function is provided that will check resultCount and return "No results." or if there are results but no item is highlighted, "resultCount results are available, use up and down arrow keys to navigate." If an item is highlighted it will run itemToString(highlightedItem) and display the value of the highlightedItem.

The object you are passed to generate your status message has the following properties:

property type description
highlightedIndex number/null The currently highlighted index
highlightedValue any The value of the highlighted item
inputValue string The current input value
isOpen boolean The isOpen state
itemToString function(any) The itemToString function (see props) for getting the string value from one of the options
previousResultCount number The total items showing in the dropdown the last time the status was updated
resultCount number The total items showing in the dropdown
selectedItem any The value of the currently selected item

onChange

function(selectedItem: any, stateAndHelpers: object) | optional, no useful default

Called when the user selects an item. Called with the item that was selected and the new state of downshift. (see onStateChange for more info on stateAndHelpers).

  • selectedItem: The item that was just selected
  • stateAndHelpers: This is the same thing your children prop function is called with (see Child Callback Function)

onStateChange

function(changes: object, stateAndHelpers: object) | optional, no useful default

This function is called anytime the internal state changes. This can be useful if you're using downshift as a "controlled" component, where you manage some or all of the state (e.g. isOpen, selectedItem, highlightedIndex, etc) and then pass it as props, rather than letting downshift control all its state itself. The parameters both take the shape of internal state ({highlightedIndex: number, inputValue: string, isOpen: boolean, selectedItem: any}) but differ slightly.

  • changes: These are the properties that actually have changed since the last state change.
  • stateAndHelpers: This is the exact same thing you're children prop function is called with (see Child Callback Function)

Tip: This function will be called any time any state is changed. The best way to determine whether any particular state was changed, you can use changes.hasOwnProperty('propName').

Note: the changes object will also have a type property that corresponds to a Downshift.stateChangeTypes property. This is an experimental feature so it's not recommended to use it if you can avoid it. If you need it, please open an issue to discuss solidifying the API.

itemCount

number | optional, defaults the number of times you call getItemProps

This is useful if you're using some kind of virtual listing component for "windowing" (like react-virtualized).

highlightedIndex

number | control prop (read more about this in the "Control Props" section below)

The index that should be highlighted

inputValue

string | control prop (read more about this in the "Control Props" section below)

The value the input should have

isOpen

boolean | control prop (read more about this in the "Control Props" section below)

Whether the menu should be considered open or closed. Some aspects of the downshift component respond differently based on this value (for example, if isOpen is true when the user hits "Enter" on the input field, then the item at the highlightedIndex item is selected).

selectedItem

any/Array(any) | control prop (read more about this in the "Control Props" section below)

The currently selected item.

children

function({}) | required

This is called with an object. Read more about the properties of this object in the section "Child Callback Function"

id

string | defaults to a generated ID

You should not normally need to set this prop. It's only useful if you're server rendering items (which each have an id prop generated based on the downshift id). For more information see the FAQ below.

environment

window | defaults to window

You should not normally need to set this prop. It's only useful if you're rendering into a different window context from where your JavaScript is running, for example an iframe.

Control Props

downshift manages its own state internally and calls your onChange and onStateChange handlers with any relevant changes. The state that downshift manages includes: isOpen, selectedItem, inputValue, and highlightedIndex. Your child callback function (read more below) can be used to manipulate this state from within the render function and can likely support many of your use cases.

However, if more control is needed, you can pass any of these pieces of state as a prop (as indicated above) and that state becomes controlled. As soon as this.props[statePropKey] !== undefined, internally, downshift will determine its state based on your prop's value rather than its own internal state. You will be required to keep the state up to date (this is where onStateChange comes in really handy), but you can also control the state from anywhere, be that state from other components, redux, react-router, or anywhere else.

Note: This is very similar to how normal controlled components work elsewhere in react (like <input />). If you want to learn more about this concept, you can learn about that from this the "Controlled Components" lecture and exercises from React Training's Advanced React course.

Child Callback Function

This is where you render whatever you want to based on the state of downshift. The function is passed as the child prop: <Downshift>{/* right here*/}</Downshift>

The properties of this object can be split into three categories as indicated below:

prop getters

These functions are used to apply props to the elements that you render. This gives you maximum flexibility to render what, when, and wherever you like. You call these on the element in question (for example: <input {...getInputProps()})). It's advisable to pass all your props to that function rather than applying them on the element yourself to avoid your props being overridden (or overriding the props returned). For example: getInputProps({onKeyUp(event) {console.log(event)}}).

property type description
getButtonProps function({}) returns the props you should apply to any menu toggle button element you render.
getInputProps function({}) returns the props you should apply to the input element that you render.
getItemProps function({}) returns the props you should apply to any menu item elements you render.
getLabelProps function({}) returns the props you should apply to the label element that you render.
getRootProps function({}) returns the props you should apply to the root element that you render. It can be optional.

getRootProps

Most of the time, you can just render a div yourself and Downshift will apply the props it needs to do its job (and you don't need to call this function). However, if you're rendering a composite component (custom component) as the root element, then you'll need to call getRootProps and apply that to your root element.

Required properties:

  • refKey: if you're rendering a composite component, that component will need to accept a prop which it forwards to the root DOM element. Commonly, folks call this innerRef. So you'd call: getRootProps({refKey: 'innerRef'}) and your composite component would forward like: <div ref={props.innerRef} />

getInputProps

This method should be applied to the input you render. It is recommended that you pass all props as an object to this method which will compose together any of the event handlers you need to apply to the input while preserving the ones that downshift needs to apply to make the input behave.

There are no required properties for this method.

getLabelProps

This method should be applied to the label you render. It is useful for ensuring that the for attribute on the <label> (htmlFor as a react prop) is the same as the id that appears on the input. If no htmlFor is provided then an ID will be generated and used for the input and the label for attribute.

There are no required properties for this method.

Note: You can definitely get by without using this (just provide an id to your input and the same htmlFor to your label and you'll be good with accessibility). However, we include this so you don't forget and it makes things a little nicer for you. You're welcome 😀

getItemProps

The props returned from calling this function should be applied to any menu items you render.

This is an impure function, so it should only be called when you will actually be applying the props to an item.

What do you mean by impure function?

Basically just don't do this:

items.map(item => {
  const props = getItemProps({item}) // we're calling it here
  if (!shouldRenderItem(item)) {
    return null // but we're not using props, and downshift thinks we are...
  }
  return <div {...props} />
})

Instead, you could do this:

items
  .filter(shouldRenderItem)
  .map(item => <div {...getItemProps({item})} />)

Required properties:

  • item: this is the item data that will be selected when the user selects a particular item.

Optional properties:

  • index: this is how downshift keeps track of your item when updating the highlightedIndex as the user keys around. By default, downshift will assume the index is the order in which you're calling getItemProps. This is often good enough, but if you find odd behavior, try setting this explicitly. It's probably best to be explicit about index when using a windowing library like react-virtualized.

getButtonProps

Call this and apply the returned props to a button. It allows you to toggle the Menu component. You can definitely build something like this yourself (all of the available APIs are exposed to you), but this is nice because it will also apply all of the proper ARIA attributes. The aria-label prop is in English. You should probably override this yourself so you can provide translations:

<button {...getButtonProps({
  'aria-label': translateWithId(isOpen ? 'close.menu' : 'open.menu'),
})} />

actions

These are functions you can call to change the state of the downshift component.

property type description
clearSelection function(cb: Function) clears the selection
clearItems function() Clears downshift's record of all the items. Only really useful if you render your items asynchronously within downshift. See #186
closeMenu function(cb: Function) closes the menu
openMenu function(cb: Function) opens the menu
selectHighlightedItem function(otherStateToSet: object, cb: Function) selects the item that is currently highlighted
selectItem function(item: any, otherStateToSet: object, cb: Function) selects the given item
selectItemAtIndex function(index: number, otherStateToSet: object, cb: Function) selects the item at the given index
setHighlightedIndex function(index: number, otherStateToSet: object, cb: Function) call to set a new highlighted index
toggleMenu function(otherStateToSet: object, cb: Function) toggle the menu open state
reset function(otherStateToSet: object, cb: Function) this resets downshift's state to a reasonable default
itemToString function(item: any) this is the same as the itemToString prop and is provided just as a helper

otherStateToSet refers to an object to set other internal state. It is recommended to avoid abusing this, but is available if you need it.

state

These are values that represent the current state of the downshift component.

property type description
highlightedIndex number / null the currently highlighted item
inputValue string / null the current value of the getInputProps input
isOpen boolean the menu open state
selectedItem any the currently selected item input

Examples

Examples exist on codesandbox.io:

If you would like to add an example, follow these steps:

  1. Fork this codesandbox
  2. Make sure your version (under dependencies) is the latest available version.
  3. Update the title and description
  4. Update the code for your example (add some form of documentation to explain what it is)
  5. Add the tag: downshift:example

You'll find other examples in the stories/examples folder of the repo. And you'll find a live version of those examples here

FAQ

How do I avoid the checksum error when server rendering (SSR)?

The checksum error you're seeing is most likely due to the automatically generated id and/or htmlFor prop you get from getInputProps and getLabelProps (respectively). It could also be from the automatically generated id prop you get from getItemProps (though this is not likely as you're probably not rendering any items when rendering a downshift component on the server).

To avoid these problems, simply provide your own id prop in getInputProps and getLabelProps. Also, you can use the id prop on the component Downshift. For example:

<Downshift id="autocomplete">
  {({getInputProps, getLabelProps}) => (
    <label {...getLabelProps({htmlFor: 'autocomplete-input'})}>
      Some Label
    </label>
    <input {...getInputProps({id: 'autocomplete-input'})} />
  )}
</Downshift>

Inspiration

I was heavily inspired by Ryan Florence. Watch his (free) lesson about "Compound Components". Initially downshift was a group of compound components using context to communicate. But then Jared Forsyth suggested I expose functions (the prop getters) to get props to apply to the elements rendered. That bit of inspiration made a big impact on the flexibility and simplicity of this API.

I also took a few ideas from the code in react-autocomplete and jQuery UI's Autocomplete.

You can watch me build the first iteration of downshift on YouTube:

You'll find more recordings of me working on downshift on my livestream YouTube playlist.

Other Solutions

You can implement these other solutions using downshift, but if you'd prefer to use these out of the box solutions, then that's fine too:

Contributors

Thanks goes to these people (emoji key):


Kent C. Dodds
💻 📖 🚇 ⚠️
Ryan Florence
🤔
Jared Forsyth
🤔 📖
Jack Moore
💡
Travis Arnold
💻 📖
Marcy Sutton
🐛 🤔
Jeremy Gayed
💡

Haroen Viaene
💡
monssef
💡
Federico Zivolo
📖
Divyendu Singh
💡
Muhammad Salman
💻
João Alberto
💻
Bernard Lin
💻 📖

Geoff Davis
💡
Anup
📖
Ferdinand Salis
🐛 💻
Kye Hohenberger
🐛
Julien Goux
🐛 💻 ⚠️
Joachim Seminck
💻
Jesse Harlin
🐛 💡

Matt Parrish
🔧
thom
💻
Vu Tran
💻
Codie Mullins
💻 💡
Mohammad Rajabifard
📖 🤔
Frank Tan
💻
Kier Borromeo
💡

Paul Veevers
💻

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

LICENSE

MIT