downshift 🏎

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

alert(`You selected ${selection.value}`)} itemToString={item => (item ? item.value : '')} > {({ getInputProps, getItemProps, getLabelProps, getMenuProps, isOpen, inputValue, highlightedIndex, selectedItem, }) => (

Enter a fruit

{item.value}

)}

` is the only component exposed by this package. It doesn't render anything itself, it just calls the render function and renders that. ["Use a render prop!"][use-a-render-prop]! `{downshift =>

/* your JSX here! */

}`. ## Basic Props This is the list of props that you should probably know about. There are some [advanced props](#advanced-props) below as well. ### children > `function({})` | _required_ This is called with an object. Read more about the properties of this object in the section "[Children Function](#children-function)". ### 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`). ### onChange > `function(selectedItem: any, stateAndHelpers: object)` | optional, no useful > default Called when the user selects an item and the selected item has changed. 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` function is called with (see [Children Function](#children-function)) ### stateReducer > `function(state: object, changes: object)` | optional **🚨 This is a really handy power feature 🚨** This function will be called each time `downshift` sets its internal state (or calls your `onStateChange` handler for control props). It allows you to modify the state change that will take place which can give you fine grain control over how the component interacts with user updates without having to use [Control Props](#control-props). It gives you the current state and the state that will be set, and you return the state that you want to set. - `state`: The full current state of downshift. - `changes`: These are the properties that are about to change. This also has a `type` property which you can learn more about in the [`stateChangeTypes`](#statechangetypes) section. ```jsx const ui = ( {/* your callback */} ) function stateReducer(state, changes) { // this prevents the menu from being closed when the user // selects an item with a keyboard or mouse switch (changes.type) { case Downshift.stateChangeTypes.keyDownEnter: case Downshift.stateChangeTypes.clickItem: return { ...changes, isOpen: state.isOpen, highlightedIndex: state.highlightedIndex, } default: return changes } } ``` > NOTE: This is only called when state actually changes. You should not attempt > to use this to handle events. If you wish to handle events, put your event > handlers directly on the elements (make sure to use the prop getters though! > For example: `` should be > ``). Also, your reducer > function should be "pure." This means it should do nothing other than return > the state changes you want to have happen. ## Advanced Props ### initialSelectedItem > `any` | defaults to `null` Pass an item or an array of items that should be selected when downshift is initialized. ### initialInputValue > `string` | defaults to `''` This is the initial input value when downshift is initialized. ### initialHighlightedIndex > `number`/`null` | defaults to `defaultHighlightedIndex` This is the initial value to set the highlighted index to when downshift is initialized. ### initialIsOpen > `boolean` | defaults to `defaultIsOpen` This is the initial `isOpen` value when downshift is initialized. ### defaultHighlightedIndex > `number`/`null` | defaults to `null` This is the value to set the `highlightedIndex` to anytime downshift is reset, when the the selection is cleared, when an item is selected or when the inputValue is changed. ### defaultIsOpen > `boolean` | defaults to `false` This is the value to set the `isOpen` to anytime downshift is reset, when the the selection is cleared, or when an item is selected. ### selectedItemChanged > `function(prevItem: any, item: any)` | defaults to: `(prevItem, item) => (prevItem !== item)` Used to determine if the new `selectedItem` has changed compared to the previous `selectedItem` and properly update Downshift's internal state. ### 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 | | `highlightedItem` | `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 | ### onSelect > `function(selectedItem: any, stateAndHelpers: object)` | optional, no useful > default Called when the user selects an item, regardless of the previous selected 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` function is called with (see [Children Function](#children-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. This also has a `type` property which you can learn more about in the [`stateChangeTypes`](#statechangetypes) section. - `stateAndHelpers`: This is the exact same thing your `children` function is called with (see [Children Function](#children-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: This is only called when state actually changes. You should not attempt > to use this to handle events. If you wish to handle events, put your event > handlers directly on the elements (make sure to use the prop getters though! > For example: `` should be > ``). ### onInputValueChange > `function(inputValue: string, stateAndHelpers: object)` | optional, no useful > default Called whenever the input value changes. Useful to use instead or in combination of `onStateChange` when `inputValue` is a controlled prop to [avoid issues with cursor positions](https://github.com/downshift-js/downshift/issues/217). - `inputValue`: The current value of the input - `stateAndHelpers`: This is the same thing your `children` function is called with (see [Children Function](#children-function)) ### 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`](https://github.com/bvaughn/react-virtualized)). ### highlightedIndex > `number` | **control prop** (read more about this in > [the Control Props section](#control-props)) The index that should be highlighted ### inputValue > `string` | **control prop** (read more about this in > [the Control Props section](#control-props)) The value the input should have ### isOpen > `boolean` | **control prop** (read more about this in > [the Control Props section](#control-props)) 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](#control-props)) The currently selected item. ### 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. ### inputId > `string` | defaults to a generated ID Used for `aria` attributes and the `id` prop of the element (`input`) you use [`getInputProps`](#getinputprops) with. ### labelId > `string` | defaults to a generated ID Used for `aria` attributes and the `id` prop of the element (`label`) you use [`getLabelProps`](#getlabelprops) with. ### menuId > `string` | defaults to a generated ID Used for `aria` attributes and the `id` prop of the element (`ul`) you use [`getMenuProps`](#getmenuprops) with. ### getItemId > `function(index)` | defaults to a function that generates an ID based on the index Used for `aria` attributes and the `id` prop of the element (`li`) you use [`getInputProps`](#getinputprops) with. ### environment > `window` | defaults to `window` This prop is only useful if you're rendering downshift within a different `window` context from where your JavaScript is running; for example, an iframe or a shadow-root. If the given context is lacking `document` and/or `add|removeEventListener` on its prototype (as is the case for a shadow-root) then you will need to pass in a custom object that is able to provide [access to these properties](https://gist.github.com/Rendez/1dd55882e9b850dd3990feefc9d6e177) for downshift. ### onOuterClick > `function(stateAndHelpers: object)` | optional A helper callback to help control internal state of downshift like `isOpen` as mentioned in [this issue](https://github.com/downshift-js/downshift/issues/206). The same behavior can be achieved using `onStateChange`, but this prop is provided as a helper because it's a fairly common use-case if you're controlling the `isOpen` state: ```jsx const ui = ( this.setState({menuIsOpen: false})} > {/* your callback */} ) ``` This callback will only be called if `isOpen` is `true`. ### scrollIntoView > `function(node: HTMLElement, menuNode: HTMLElement)` | defaults to internal > implementation This allows you to customize how the scrolling works when the highlighted index changes. It receives the node to be scrolled to and the root node (the root node you render in downshift). Internally we use [`compute-scroll-into-view`](https://www.npmjs.com/package/compute-scroll-into-view) so if you use that package then you wont be adding any additional bytes to your bundle :) ## stateChangeTypes There are a few props that expose changes to state ([`onStateChange`](#onstatechange) and [`stateReducer`](#statereducer)). For you to make the most of these APIs, it's important for you to understand why state is being changed. To accomplish this, there's a `type` property on the `changes` object you get. This `type` corresponds to a `Downshift.stateChangeTypes` property. The list of all possible values this `type` property can take is defined in [this file](https://github.com/downshift-js/downshift/blob/master/src/stateChangeTypes.js) and is as follows: - `Downshift.stateChangeTypes.unknown` - `Downshift.stateChangeTypes.mouseUp` - `Downshift.stateChangeTypes.itemMouseEnter` - `Downshift.stateChangeTypes.keyDownArrowUp` - `Downshift.stateChangeTypes.keyDownArrowDown` - `Downshift.stateChangeTypes.keyDownEscape` - `Downshift.stateChangeTypes.keyDownEnter` - `Downshift.stateChangeTypes.clickItem` - `Downshift.stateChangeTypes.blurInput` - `Downshift.stateChangeTypes.changeInput` - `Downshift.stateChangeTypes.keyDownSpaceButton` - `Downshift.stateChangeTypes.clickButton` - `Downshift.stateChangeTypes.blurButton` - `Downshift.stateChangeTypes.controlledPropUpdatedSelectedItem` - `Downshift.stateChangeTypes.touchEnd` See [`stateReducer`](#statereducer) for a concrete example on how to use the `type` property. ## 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 Children function (read more below) can be used to manipulate this state 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 ``). If you want to learn more about this concept, you > can learn about that from this the > [Advanced React Component Patterns course](#advanced-react-component-patterns-course) ## Children Function This is where you render whatever you want to based on the state of `downshift`. You use it like so: ```javascript const ui = ( {downshift => ( // use downshift utilities and state here, like downshift.isOpen, // downshift.getInputProps, etc.

{/* more jsx here */}

)} ) ``` The properties of this `downshift` object can be split into three categories as indicated below: ### prop getters > See > [the blog post about prop getters](https://blog.kentcdodds.com/how-to-give-rendering-control-to-users-with-prop-getters-549eaef76acf) > NOTE: These prop-getters provide important `aria-` attributes which are very > important to your component being accessible. It's recommended that you > utilize these functions and apply the props they give you to your components. 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: ` | property | type | description | | ---------------------- | ----------------- | ---------------------------------------------------------------------------------------------- | | `getToggleButtonProps` | `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. | | `getMenuProps` | `function({},{})` | returns the props you should apply to the `ul` element (or root of your menu) that you render. | | `getRootProps` | `function({},{})` | returns the props you should apply to the root element that you render. It can be optional. | #### `getRootProps`

If you cannot render a div as the root element, then read this

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 (downshift will throw an error otherwise). There are no required properties for this method. Optional 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: `

` If you're rendering a composite component, `Downshift` checks that `getRootProps` is called and that `refKey` is a prop of the returned composite component. This is done to catch common causes of errors but, in some cases, the check could fail even if the ref is correctly forwarded to the root DOM component. In these cases, you can provide the object `{suppressRefError : true}` as the second argument to `getRootProps` to completely bypass the check.\ **Please use it with extreme care and only if you are absolutely sure that the ref is correctly forwarded otherwise `Downshift` will unexpectedly fail.**\ See [#235](https://github.com/downshift-js/downshift/issues/235) for the discussion that lead to this.

#### `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. Optional properties: - `disabled`: If this is set to true, then no event handlers will be returned from `getInputProps` and a `disabled` prop will be returned (effectively disabling the input). #### `getLabelProps` This method should be applied to the `label` you render. It is useful for ensuring that the `for` attribute on the `` (`htmlFor` as a react prop) is the same as the `id` that appears on the `input`. If no `htmlFor` is provided (the normal case) 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: For accessibility purposes, calling this method is highly recommended. #### `getMenuProps` This method should be applied to the element which contains your list of items. Typically, this will be a `

` or a `

`, there is no need to specify this property. Please keep in mind that menus, for accessiblity purposes, should always be rendered, regardless of whether you hide it or not. Otherwise, `getMenuProps` may throw error if you unmount and remount the menu. - `aria-label`: By default the menu will add an `aria-labelledby` that refers to the `` rendered with `getLabelProps`. However, if you provide `aria-label` to give a more specific label that describes the options available, then `aria-labelledby` will not be provided and screen readers can use your `aria-label` instead. In some cases, you might want to completely bypass the `refKey` check. Then you can provide the object `{suppressRefError : true}` as the second argument to `getMenuProps`. **Please use it with extreme care and only if you are absolutely sure that the ref is correctly forwarded otherwise `Downshift` will unexpectedly fail.** ```jsx

{item.name}

``` > Note that for accessibility reasons it's best if you always render this > element whether or not downshift is in an `isOpen` state. #### `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: ```jsx 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

}) ``` Instead, you could do this: ```jsx items.filter(shouldRenderItem).map(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`. - `disabled`: If this is set to `true`, then all of the downshift item event handlers will be omitted. Items will not be highlighted when hovered, and items will not be selected when clicked. #### `getToggleButtonProps` 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. Optional properties: - `disabled`: If this is set to `true`, then all of the downshift button event handlers will be omitted (it wont toggle the menu when clicked). - `aria-label`: The `aria-label` prop is in English. You should probably override this yourself so you can provide translations: ```jsx const myButton = (