alphagovAccessible autocomplete
The accessible autocomplete is a component that helps users choose answers from a list you provide. You can also use it to make the answers you get from users more consistent.
If you're asking users to provide their country or territory, the govuk-country-and-territory-autocomplete might be more appropriate.
accessible-autocomplete is a JavaScript autocomplete built from the ground up to be accessible. The design goals are:
- Accessibility: Following WAI-ARIA best practices and testing with assistive technologies.
- User experience: Supporting a wide variety of user needs.
- Compatibility: Working with recommended browsers and assistive technologies.
Support
The GOV.UK Design System team maintains the accessible autocomplete as a standalone component. However, we’re only able to put in minimal work to support it.
Read about our plans to maintain this component.
Read more about the types of support we can provide.
Installation / usage
Using npm and a module system
Install it by running:
npm install --save accessible-autocompleteThe accessibleAutocomplete function will render an autocomplete <input> and its accompanying suggestions and aria-live region. Your page should provide a <label> and a container element:
<label for="my-autocomplete">Select your country</label>
<div id="my-autocomplete-container"></div>Then import it using a module system like Browserify / Webpack / Rollup, and call the accessibleAutocomplete function, providing an array of values:
import accessibleAutocomplete from 'accessible-autocomplete'
const countries = [
'France',
'Germany',
'United Kingdom'
]
accessibleAutocomplete({
element: document.querySelector('#my-autocomplete-container'),
id: 'my-autocomplete', // To match it to the existing <label>.
source: countries
})If you want to use it as a replacement for a <select> element, read the Progressive enhancement section.
As a plain JavaScript module
You can copy the dist/accessible-autocomplete.min.js file to your JavaScript folder and import it into the browser:
<script type="text/javascript" src="assets/js/accessible-autocomplete.min.js"></script>Styling the autocomplete
A stylesheet is included with the package at dist/accessible-autocomplete.min.css.
You can copy it to your stylesheets folder and import it into the browser:
<link rel="stylesheet" href="assets/css/accessible-autocomplete.min.css" />You can also import it using Sass:
@import "accessible-autocomplete";[!NOTE]
When styling the
.autocomplete__inputelement, be aware that theautoselectoption will render a second.autocomplete__hintinput element for suggestion text. Both elements should be styled to ensure suggestions exactly align with the typed input text.
Using with Preact
If you already use Preact in your application, you can import a bundle that will use that:
import preact from 'preact'
import Autocomplete from 'accessible-autocomplete/preact'
preact.render(
<Autocomplete id='autocomplete' source={suggest} />,
document.querySelector('#container')
)Preact versions
Preact v8.5.3 has been tested to work with the Accessible Autocomplete - although make sure to check out documented issues.
Preact 10.19.6 has been incompletely tested with the Accessible Autocomplete. No issues were found in Chrome and Firefox, but our automated tests for picking an option using the keyboard failed in Internet Explorer 11 (an issue we could not replicate when testing manually, though).
We recommend you carry out thorough testing if you wish to use this or later versions of Preact.
Using with React
If you already use React in your application, you can import a bundle that will use that:
import React from 'react'
import ReactDOM from 'react-dom'
import Autocomplete from 'accessible-autocomplete/react'
ReactDOM.render(
<Autocomplete id='autocomplete' source={suggest} />,
document.querySelector('#container')
)React versions
React v15.5.4 has been tested to work with the Accessible Autocomplete - although make sure to check out documented issues.
React v15.6.2, v16.14.0, v17.0.2, and v18.2.0 have been incompletely tested with the Accessible Autocomplete. No undocumented issues were found (though be aware that React 18 dropped support for Internet Explorer)
We recommend you carry out thorough testing if you wish to use this or later versions of React.
API documentation
Required options
element
Type: HTMLElement
The container element in which the autocomplete will be rendered in.
id
Type: string
The id to assign to the autocomplete input field, to use with a <label for=id>. Not required if using enhanceSelectElement.
source
Type: Array | Function
An array of values to search when the user types in the input field, or a function to take what the user types and call a callback function with the results to be displayed.
An example of an array of values:
const countries = [
'France',
'Germany',
'United Kingdom'
]If source is a function, the arguments are: query: string, populateResults: Function
Similar to the source argument for typeahead.js, a backing data source for suggestions. query is what gets typed into the input field, which will callback to populateResults synchronously with the array of string results to display in the menu.
An example of a simple suggestion engine:
function suggest (query, populateResults) {
const results = [
'France',
'Germany',
'United Kingdom'
]
const filteredResults = results.filter(result => result.indexOf(query) !== -1)
populateResults(filteredResults)
}Other options
inputClasses (default: null)
Type: string | null
Adds custom html classes to the generated input element.
If autoselect is set to true, the option hintClasses can be configured separately or it will default to the inputClasses value.
hintClasses (default: null)
Type: string | null
Adds custom html classes to the additional input element that appears when what the user typed matches the start of a suggestion.
If autoselect is set to true, the option inputClasses will be used as the default value unless hintClasses is set to an empty string ''.
menuAttributes (default: {})
Type: Object
Sets html attributes and their values on the generated ul menu element. Useful for adding aria-labelledby and setting to the value of the id attribute on your existing label, to provide context to an assistive technology user.
[!NOTE]
To maintain assistive technology support, menu attributes
id,roleandonMouseLeavecannot be overridden usingmenuAttributes. SettingclassNamewill append to the component default andmenuClassesvalues.
menuClasses (default: null)
Type: string | null
Adds custom html classes to the generated ul menu element.
autoselect (default: false)
Type: Boolean
Set to true to highlight the first option when the user types in something and receives results. Pressing enter will select it.
confirmOnBlur (default: true)
Type: Boolean
The autocomplete will confirm the currently selected option when the user clicks outside of the component. Set to false to disable.
cssNamespace (default: 'autocomplete')
Type: string
Use this property to override the BEM block name that the JavaScript component will use. You will need to rewrite the CSS class names to use your specified block name.
defaultValue (default: '')
Type: string
Specify a string to prefill the autocomplete with.
displayMenu (default: 'inline')
Type: 'inline' | 'overlay'
You can set this property to specify the way the menu should appear, whether inline or as an overlay.
minLength (default: 0)
Type: number
The minimum number of characters that should be entered before the autocomplete will attempt to suggest options. When the query length is under this, the aria status region will also provide helpful text to the user informing them they should type in more.
name (default: 'input-autocomplete')
Type: string
The name for the autocomplete input field, to use with a parent <form>.
onConfirm (default: () => {})
Type: Function
Arguments: confirmed: Object
This function will be called when the user confirms an option, with the option they've confirmed.
placeholder (default: '') :warning: not recommended :warning:
Type: string
This option will populate the placeholder attribute on the input element.
We think placeholders have usability issues and that there are better alternatives to input placeholder text, so we do not recommend using this option.
required (default: false)
Type: Boolean
The input field will be rendered with a required attribute, see W3C required attribute definition.
showAllValues (default: false)
Type: Boolean
If this is set to true, all values are shown when the user clicks the input. This is similar
to a default dropdown, so the autocomplete is rendered with a dropdown arrow to convey
this behaviour.
showNoOptionsFound (default: true)
Type: Boolean
The autocomplete will display a "No results found" template when there are no results. Set to false to disable.
templates (default: undefined)
Type:
{
inputValue: Function,
suggestion: Function
}This object defines templates (functions) that are used for displaying parts of the autocomplete.
inputValue is a function that receives one argument, the currently selected suggestion. It returns the string value to be inserted into the input.
suggestion is a function that receives one argument, a suggestion to be displayed. It is used when rendering suggestions, and should return a string, which can contain HTML.
:warning: Caution: because this function allows you to output arbitrary HTML, you should make sure it's trusted, and accessible.
If your template includes child elements with defined foreground or background colours, check they display correctly in forced colors modes. For example, Windows high contrast mode.
dropdownArrow (default: A triangle pointing down)
Type: Function
A function that gets passed an object with the property className ({ className: '' }) and should return a string of HTML or a (P)React element. :warning: Caution: because this function allows you to output arbitrary HTML, you should make sure it's trusted, and accessible.
Internationalization
tNoResults (default: () => 'No results found')
Type: Function
A function that receives no arguments and returns the text used in the dropdown to indicate that there are no results.
tStatusQueryTooShort (default: (minQueryLength) => `Type in ${minQueryLength} or more characters for results`)
Type: Function
A function that receives one argument that indicates the minimal amount of characters needed for the dropdown to trigger and returns the text used in the accessibility hint to indicate that the query is too short.
tStatusNoResults (default: () => 'No search results')
Type: Function
A function that receives no arguments and returns the text that is used in the accessibility hint to indicate that there are no results.
tStatusSelectedOption (default: (selectedOption, length, index) => `${selectedOption} ${index + 1} of ${length} is highlighted`)
Type: Function
A function that receives three arguments - the selectedOption, the count of available options, and the (zero-based) index of the selected option - and returns the text used in the accessibility hint to indicate which option is selected.
tStatusResults
Default:
(length, contentSelectedOption) => {
const words = {
result: (length === 1) ? 'result' : 'results',
is: (length === 1) ? 'is' : 'are'
}
return <span>{length} {words.result} {words.is} available. {contentSelectedOption}</span>
}Type: Function
A function that receives two arguments - the count of available options and the return value of tStatusSelectedOption - and returns the text used in the accessibility hint to indicate which options are available and which is selected.
tAssistiveHint (default: () => 'When autocomplete results are available use up and down arrows to review and enter to select. Touch device users, explore by touch or with swipe gestures.')
Type: Function
A function that receives no arguments and returns the text to be assigned as the aria description of the html input element, via the aria-describedby attribute.
This text is intended as an initial instruction to the assistive tech user. The aria-describedby attribute is automatically removed once user input is detected, in order to reduce screen reader verbosity.
Progressive enhancement
If your autocomplete is meant to select from a small list of options (a few hundred), we strongly suggest that you render a <select> menu on the server, and use progressive enhancement.
If you have the following HTML:
<select id="location-picker">
<option value="fr">France</option>
<option value="de">Germany</option>
<option value="gb">United Kingdom</option>
</select>You can use the accessibleAutocomplete.enhanceSelectElement function to enhance it into an autocomplete:
accessibleAutocomplete.enhanceSelectElement({
selectElement: document.querySelector('#location-picker')
})This will:
- Place an autocomplete input field after the specified
<select> - Default the autocomplete
autoselecttotrue - Default the autocomplete
defaultValueto the select'soption[selected] - Default the autocomplete
idto the<select>'sid - Default the autocomplete
nameattribute to''to prevent it being included in form submissions - Default the autocomplete
sourceto use existing<option>s from the<select> - Hide the
<select>using inlinedisplay: none - Set the
<select>'sidto${id}-selectto decouple from any<label> - Upon confirming a value in the autocomplete, update the original
<select>
This function takes the same options as accessibleAutocomplete, with the only difference being that it uses selectElement instead of element, which needs to be an instance of HTMLSelectElement.
Note: The
accessibleAutocomplete.enhanceSelectElementfunction is fairly light and wraps the public API foraccessibleAutocomplete. If your use case doesn't fit the above defaults, try reading the source and seeing if you can write your own.
Null options
If your <select> element has a "null" option - a default option with no value - then you can pass a defaultValue option to enhanceSelectElement which will replace the label of this option when it is selected.
With the following HTML:
<select id="location-picker">
<option value="">Select a country</option>
<option value="fr">France</option>
<option value="de">Germany</option>
<option value="gb">United Kingdom</option>
</select>Then passing a defaultValue option of '' will then leave the autocomplete blank if the null option is selected.
accessibleAutocomplete.enhanceSelectElement({
defaultValue: '',
selectElement: document.querySelector('#location-picker')
})Any null options will also be filtered out of the options used to populate the source of the autocomplete element. To preserve options with no value in the autocomplete, then pass a preserveNullOptions flag of true to enhanceSelectElement.
Analytics and tracking
The following events get triggered on the input element during the life cycle of the autocomplete:
onConfirm- This function will be called when the user confirms an option, with the option they've chosen.
Example usage:
accessibleAutocomplete({
// additional options
onConfirm: (val) => {
track(val)
}
})Why another autocomplete?
accessible-autocomplete was built after studying many existing solutions and prototyping patches to fix user experience or accessibility issues. It draws heavy inspiration from the following (and a lot of others):
- ljwatson/design-patterns: great accessible experience
- corejavascript/corejs-typeahead: flexible autocomplete/suggestion engine architecture
- JamieAppleseed/selectToAutocomplete: ease of use
Developing locally
Check out the CONTRIBUTING guide for instructions.
If you want to help and want to get more familiar with the codebase, try starting with the "good for beginners" issues.
License
MIT.