Compose

The compose package is a collection of handy Hooks and Higher Order Components (HOCs) you can use to wrap your WordPress components and provide some basic features like: state, instance id, pure...

The compose function is inspired by flowRight from Lodash and works the same way. It comes from functional programming, and allows you to compose any number of functions. You might also think of this as layering functions; compose will execute the last function first, then sequentially move back through the previous functions passing the result of each function upward.

An example that illustrates it for two functions:

const compose = ( f, g ) => x
    => f( g( x ) );

Here's a simplified example of compose in use from Gutenberg's PluginSidebar component:

Using compose:

const applyWithSelect = withSelect( ( select, ownProps ) => {
	return doSomething( select, ownProps );
} );
const applyWithDispatch = withDispatch( ( dispatch, ownProps ) => {
	return doSomethingElse( dispatch, ownProps );
} );

export default compose(
	withPluginContext,
	applyWithSelect,
	applyWithDispatch
)( PluginSidebarMoreMenuItem );

Without compose, the code would look like this:

const applyWithSelect = withSelect( ( select, ownProps ) => {
	return doSomething( select, ownProps );
} );
const applyWithDispatch = withDispatch( ( dispatch, ownProps ) => {
	return doSomethingElse( dispatch, ownProps );
} );

export default withPluginContext(
	applyWithSelect( applyWithDispatch( PluginSidebarMoreMenuItem ) )
);

Installation

Install the module

npm install @wordpress/compose --save

This package assumes that your code will run in an ES2015+ environment. If you're using an environment that has limited or no support for such language features and APIs, you should include the polyfill shipped in @wordpress/babel-preset-default in your code.

API

For more details, you can refer to each Higher Order Component's README file. Available components are located here.

compose

Composes multiple higher-order components into a single higher-order component. Performs right-to-left function composition, where each successive invocation is supplied the return value of the previous.

This is inspired by lodash's flowRight function.

Related

• https://lodash.com/docs/4#flow-right

createHigherOrderComponent

Given a function mapping a component to an enhanced component and modifier name, returns the enhanced component augmented with a generated displayName.

Parameters

• mapComponent ( Inner: TInner ) => TOuter: Function mapping component to enhanced component.
• modifierName string: Seed name from which to generated display name.

Returns

• Component class with generated display name assigned.

debounce

A simplified and properly typed version of lodash's debounce, that always uses timers instead of sometimes using rAF.

Creates a debounced function that delays invoking func until after wait milliseconds have elapsed since the last time the debounced function was invoked. The debounced function comes with a cancel method to cancel delayed func invocations and a flush method to immediately invoke them. Provide options to indicate whether func should be invoked on the leading and/or trailing edge of the wait timeout. The func is invoked with the last arguments provided to the debounced function. Subsequent calls to the debounced function return the result of the last func invocation.

Note: If leading and trailing options are true, func is invoked on the trailing edge of the timeout only if the debounced function is invoked more than once during the wait timeout.

If wait is 0 and leading is false, func invocation is deferred until the next tick, similar to setTimeout with a timeout of 0.

Parameters

• func Function: The function to debounce.
• wait number: The number of milliseconds to delay.
• options Partial< DebounceOptions >: The options object.
• options.leading boolean: Specify invoking on the leading edge of the timeout.
• options.maxWait number: The maximum time func is allowed to be delayed before it's invoked.
• options.trailing boolean: Specify invoking on the trailing edge of the timeout.

Returns

• Returns the new debounced function.

ifCondition

Higher-order component creator, creating a new component which renders if the given condition is satisfied or with the given optional prop name.

Usage

type Props = { foo: string };
const Component = ( props: Props ) => <div>{ props.foo }</div>;
const ConditionalComponent = ifCondition( ( props: Props ) => props.foo.length !== 0 )( Component );
<ConditionalComponent foo="" />; // => null
<ConditionalComponent foo="bar" />; // => <div>bar</div>;

Parameters

• predicate ( props: Props ) => boolean: Function to test condition.

Returns

• Higher-order component.

observableMap

A constructor (factory) for ObservableMap, a map-like key/value data structure where the individual entries are observable: using the subscribe method, you can subscribe to updates for a particular keys. Each subscriber always observes one specific key and is not notified about any unrelated changes (for different keys) in the ObservableMap.

Returns

• ObservableMap< K, V >: A new instance of the ObservableMap type.

pipe

Composes multiple higher-order components into a single higher-order component. Performs left-to-right function composition, where each successive invocation is supplied the return value of the previous.

This is inspired by lodash's flow function.

Related

• https://lodash.com/docs/4#flow

pure

Deprecated Use memo or PureComponent instead.

Given a component returns the enhanced component augmented with a component only re-rendering when its props/state change

throttle

A simplified and properly typed version of lodash's throttle, that always uses timers instead of sometimes using rAF.

Creates a throttled function that only invokes func at most once per every wait milliseconds. The throttled function comes with a cancel method to cancel delayed func invocations and a flush method to immediately invoke them. Provide options to indicate whether func should be invoked on the leading and/or trailing edge of the wait timeout. The func is invoked with the last arguments provided to the throttled function. Subsequent calls to the throttled function return the result of the last func invocation.

Note: If leading and trailing options are true, func is invoked on the trailing edge of the timeout only if the throttled function is invoked more than once during the wait timeout.

If wait is 0 and leading is false, func invocation is deferred until the next tick, similar to setTimeout with a timeout of 0.

Parameters

• func Function: The function to throttle.
• wait number: The number of milliseconds to throttle invocations to.
• options Partial< ThrottleOptions >: The options object.
• options.leading boolean: Specify invoking on the leading edge of the timeout.
• options.trailing boolean: Specify invoking on the trailing edge of the timeout.

Returns

• Returns the new throttled function.

useAsyncList

React hook returns an array which items get asynchronously appended from a source array. This behavior is useful if we want to render a list of items asynchronously for performance reasons.

Parameters

• list T[]: Source array.
• config AsyncListConfig: Configuration object.

Returns

• T[]: Async array.

useConstrainedTabbing

In Dialogs/modals, the tabbing must be constrained to the content of the wrapper element. This hook adds the behavior to the returned ref.

Usage

import { useConstrainedTabbing } from '@wordpress/compose';

const ConstrainedTabbingExample = () => {
	const constrainedTabbingRef = useConstrainedTabbing();
	return (
		<div ref={ constrainedTabbingRef }>
			<Button />
			<Button />
		</div>
	);
};

Returns

• import('react').RefCallback<Element>: Element Ref.

useCopyOnClick

Deprecated

Copies the text to the clipboard when the element is clicked.

Parameters

• ref import('react').RefObject<string | Element | NodeListOf<Element>>: Reference with the element.
• text string|Function: The text to copy.
• timeout [number]: Optional timeout to reset the returned state. 4 seconds by default.

Returns

• boolean: Whether or not the text has been copied. Resets after the timeout.

useCopyToClipboard

Copies the given text to the clipboard when the element is clicked.

Parameters

• text string | (() => string): The text to copy. Use a function if not already available and expensive to compute.
• onSuccess Function: Called when to text is copied.

Returns

• import('react').Ref<TElementType>: A ref to assign to the target element.

useDebounce

Debounces a function similar to Lodash's debounce. A new debounced function will be returned and any scheduled calls cancelled if any of the arguments change, including the function to debounce, so please wrap functions created on render in components in useCallback.

Related

• https://lodash.com/docs/4#debounce

Parameters

• fn TFunc: The function to debounce.
• wait [number]: The number of milliseconds to delay.
• options [import('../../utils/debounce').DebounceOptions]: The options object.

Returns

• import('../../utils/debounce').DebouncedFunc<TFunc>: Debounced function.

useDebouncedInput

Helper hook for input fields that need to debounce the value before using it.

Parameters

• defaultValue The default value to use.

Returns

• [ string, ( value: string ) => void, string ]: The input value, the setter and the debounced input value.

useDisabled

In some circumstances, such as block previews, all focusable DOM elements (input fields, links, buttons, etc.) need to be disabled. This hook adds the behavior to disable nested DOM elements to the returned ref.

If you can, prefer the use of the inert HTML attribute.

Usage

import { useDisabled } from '@wordpress/compose';

const DisabledExample = () => {
	const disabledRef = useDisabled();
	return (
		<div ref={ disabledRef }>
			<a href="#">This link will have tabindex set to -1</a>
			<input
				placeholder="This input will have the disabled attribute added to it."
				type="text"
			/>
		</div>
	);
};

Parameters

• config Object: Configuration object.
• config.isDisabled boolean=: Whether the element should be disabled.

Returns

• import('react').RefCallback<HTMLElement>: Element Ref.

useEvent

Creates a stable callback function that has access to the latest state and can be used within event handlers and effect callbacks. Throws when used in the render phase.

Usage

function Component( props ) {
	const onClick = useEvent( props.onClick );
	useEffect( () => {
		onClick();
		// Won't trigger the effect again when props.onClick is updated.
	}, [ onClick ] );
	// Won't re-render Button when props.onClick is updated (if `Button` is
	// wrapped in `React.memo`).
	return <Button onClick={ onClick } />;
}

Parameters

• callback T: The callback function to wrap.

useFocusableIframe

Dispatches a bubbling focus event when the iframe receives focus. Use onFocus as usual on the iframe or a parent element.

Returns

• RefCallback< HTMLIFrameElement >: Ref to pass to the iframe.

useFocusOnMount

Hook used to focus the first tabbable element on mount.

Usage

import { useFocusOnMount } from '@wordpress/compose';

const WithFocusOnMount = () => {
	const ref = useFocusOnMount();
	return (
		<div ref={ ref }>
			<Button />
			<Button />
		</div>
	);
};

Parameters

• focusOnMount boolean | 'firstElement': Focus on mount mode.

Returns

• import('react').RefCallback<HTMLElement>: Ref callback.

useFocusReturn

Adds the unmount behavior of returning focus to the element which had it previously as is expected for roles like menus or dialogs.

Usage

import { useFocusReturn } from '@wordpress/compose';

const WithFocusReturn = () => {
	const ref = useFocusReturn();
	return (
		<div ref={ ref }>
			<Button />
			<Button />
		</div>
	);
};

Parameters

• onFocusReturn [() => void]: Overrides the default return behavior.

Returns

• import('react').RefCallback<HTMLElement>: Element Ref.

useInstanceId

Provides a unique instance ID.

Parameters

• object object: Object reference to create an id for.
• prefix [string]: Prefix for the unique id.
• preferredId [string | number]: Default ID to use.

Returns

• string | number: The unique instance id.

useIsomorphicLayoutEffect

Preferred over direct usage of useLayoutEffect when supporting server rendered components (SSR) because currently React throws a warning when using useLayoutEffect in that environment.

useKeyboardShortcut

Attach a keyboard shortcut handler.

Related

• https://craig.is/killing/mice#api.bind for information about the callback parameter.

Parameters

• shortcuts string[]|string: Keyboard Shortcuts.
• callback (e: import('mousetrap').ExtendedKeyboardEvent, combo: string) => void: Shortcut callback.
• options WPKeyboardShortcutConfig: Shortcut options.

useMediaQuery

Runs a media query and returns its value when it changes.

Parameters

• query [string]: Media Query.

Returns

• boolean: return value of the media query.

useMergeRefs

Merges refs into one ref callback.

It also ensures that the merged ref callbacks are only called when they change (as a result of a useCallback dependency update) OR when the ref value changes, just as React does when passing a single ref callback to the component.

As expected, if you pass a new function on every render, the ref callback will be called after every render.

If you don't wish a ref callback to be called after every render, wrap it with useCallback( callback, dependencies ). When a dependency changes, the old ref callback will be called with null and the new ref callback will be called with the same value.

To make ref callbacks easier to use, you can also pass the result of useRefEffect, which makes cleanup easier by allowing you to return a cleanup function instead of handling null.

It's also possible to disable a ref (and its behaviour) by simply not passing the ref.

const ref = useRefEffect( ( node ) => {
  node.addEventListener( ... );
  return () => {
    node.removeEventListener( ... );
  };
}, [ ...dependencies ] );
const otherRef = useRef();
const mergedRefs useMergeRefs( [
  enabled && ref,
  otherRef,
] );
return <div ref={ mergedRefs } />;

Parameters

• refs Array<TRef>: The refs to be merged.

Returns

• import('react').RefCallback<TypeFromRef<TRef>>: The merged ref callback.

useObservableValue

React hook that lets you observe an entry in an ObservableMap. The hook returns the current value corresponding to the key, or undefined when there is no value stored. It also observes changes to the value and triggers an update of the calling component in case the value changes.

Parameters

• map ObservableMap< K, V >: The ObservableMap to observe.
• name K: The map key to observe.

Returns

• V | undefined: The value corresponding to the map key requested.

usePrevious

Use something's value from the previous render. Based on https://usehooks.com/usePrevious/.

Parameters

• value T: The value to track.

Returns

• T | undefined: The value from the previous render.

useReducedMotion

Hook returning whether the user has a preference for reduced motion.

Returns

• boolean: Reduced motion preference value.

useRefEffect

Effect-like ref callback. Just like with useEffect, this allows you to return a cleanup function to be run if the ref changes or one of the dependencies changes. The ref is provided as an argument to the callback functions. The main difference between this and useEffect is that the useEffect callback is not called when the ref changes, but this is. Pass the returned ref callback as the component's ref and merge multiple refs with useMergeRefs.

It's worth noting that if the dependencies array is empty, there's not strictly a need to clean up event handlers for example, because the node is to be removed. It is necessary if you add dependencies because the ref callback will be called multiple times for the same node.

Parameters

• callback ( node: TElement ) => ( () => void ) | void: Callback with ref as argument.
• dependencies DependencyList: Dependencies of the callback.

Returns

• RefCallback< TElement | null >: Ref callback.

useResizeObserver

Sets up a ResizeObserver for an HTML or SVG element.

Pass the returned setter as a callback ref to the React element you want to observe, or use it in layout effects for advanced use cases.

Usage

const setElement = useResizeObserver(
	( resizeObserverEntries ) => console.log( resizeObserverEntries ),
	{ box: 'border-box' }
);
<div ref={ setElement } />;

// The setter can be used in other ways, for example:
useLayoutEffect( () => {
	setElement( document.querySelector( `data-element-id="${ elementId }"` ) );
}, [ elementId ] );

Parameters

• callback ResizeObserverCallback: The ResizeObserver callback - MDN docs.
• options ResizeObserverOptions: Options passed to ResizeObserver.observe when called - MDN docs. Changes will be ignored.

useStateWithHistory

useState with undo/redo history.

Parameters

• initialValue T: Initial value.

Returns

• Value, setValue, hasUndo, hasRedo, undo, redo.

useThrottle

Throttles a function similar to Lodash's throttle. A new throttled function will be returned and any scheduled calls cancelled if any of the arguments change, including the function to throttle, so please wrap functions created on render in components in useCallback.

Related

• https://lodash.com/docs/4#throttle

Parameters

• fn TFunc: The function to throttle.
• wait [number]: The number of milliseconds to throttle invocations to.
• options [import('../../utils/throttle').ThrottleOptions]: The options object. See linked documentation for details.

Returns

• import('../../utils/debounce').DebouncedFunc<TFunc>: Throttled function.

useViewportMatch

Returns true if the viewport matches the given query, or false otherwise.

Usage

useViewportMatch( 'huge', '<' );
useViewportMatch( 'medium' );

Parameters

• breakpoint WPBreakpoint: Breakpoint size name.
• operator [WPViewportOperator]: Viewport operator.

Returns

• boolean: Whether viewport matches query.

useWarnOnChange

Hook that performs a shallow comparison between the preview value of an object and the new one, if there's a difference, it prints it to the console. this is useful in performance related work, to check why a component re-renders.

Usage

function MyComponent( props ) {
	useWarnOnChange( props );

	return 'Something';
}

Parameters

• object object: Object which changes to compare.
• prefix string: Just a prefix to show when console logging.

withGlobalEvents

Deprecated

Higher-order component creator which, given an object of DOM event types and values corresponding to a callback function name on the component, will create or update a window event handler to invoke the callback when an event occurs. On behalf of the consuming developer, the higher-order component manages unbinding when the component unmounts, and binding at most a single event handler for the entire application.

Parameters

• eventTypesToHandlers Record<keyof GlobalEventHandlersEventMap, string>: Object with keys of DOM event type, the value a name of the function on the original component's instance which handles the event.

Returns

• any: Higher-order component.

withInstanceId

A Higher Order Component used to provide a unique instance ID by component.

withSafeTimeout

A higher-order component used to provide and manage delayed function calls that ought to be bound to a component's lifecycle.

withState

Deprecated Use useState instead.

A Higher Order Component used to provide and manage internal component state via props.

Parameters

• initialState any: Optional initial state of the component.

Returns

• any: A higher order component wrapper accepting a component that takes the state props + its own props + setState and returning a component that only accepts the own props.

Contributing to this package

This is an individual package that's part of the Gutenberg project. The project is organized as a monorepo. It's made up of multiple self-contained software packages, each with a specific purpose. The packages in this monorepo are published to npm and used by WordPress as well as other software projects.

To find out more about contributing to this package or Gutenberg as a whole, please read the project's main contributor guide.