hooks

Hooks

Installation

Yarn

yarn add @leafygreen-ui/hooks

NPM

npm install @leafygreen-ui/hooks

useEventListener

Hook to create and remove eventListeners

Example

import { useEventListener } from '@leafygreen-ui/hooks';

useEventListener('click', handleClick, { enabled });

Properties

Prop	Type	Description	Default
type	Global Event Handler, string	Type of event to listen for.
eventCallback	function	Callback executed when event is triggered.
optional	object	Optional third argument passed to function with implementation specifications.
optional.options	AddEventListenerOptions excluding once	Parameter to specify options passed to the eventListener. To enable the once option, see optional.enabled.
optional.enabled	boolean, 'once'	Determines whether the event handler is attached or not. Setting this to "once" will ensure the event handler will be detached after the initial time an event is triggered.	true
optional.dependencies	Array	Array to be passed to useEffect hook, such that the hook will only run if the array's values have changed.	[enabled, type]
optional.element	Document, HTMLElement	The DOM node to attach the event handler to. Defaults to document.	document

useEscapeKey

Hook that listens for EscapeKey press.

Example

import { useEscapeKey } from '@leafygreen-ui/hooks';

useEscapeKey(handleEscapeCallback);

Properties

Prop	Type	Description	Default
callback	function	Callback executed when EscapeKey is pressed.
optional	object	Optional argument passed to function with implementation specifications. See supported parameters for useEventHandler.

useMutationObserver

Example

import { useMutationObserver } from '@leafygreen-ui/hooks';

const lastTimeContentElMutated = useMutationObserver(
  target,
  mutationOptions,
  () => Date.now(),
  adjustOnMutation,
);

Properties

Prop	Type	Description	Default
target	HTMLElement, null	HTMLElement to subscribe to changes to.
options	MutationObserverInit	Object with information about what DOM changes to subscribe to. Docs here
callback	function	Callback function to execute inside of MutationObserver instance.
enabled	boolean	Determines whether the event handler is attached or not.	true

useViewportSize

Hook to subscribe to changes in viewport size

Example

const viewportSize = useViewportSize();

usePoller

Hook to create a Poller that polls at a given interval.

If your onPoll handler returns a Promise it will wait for the Promise to resolve or reject before scheduling the next interval.

This hooks also makes use of the Page Visibility API. If the page is hidden then polling will stop. When a page becomes visible again then polling will resume.

Example

import { usePoller } from '@leafygreen-ui/hooks';

usePoller(onPoll, {
  interval: 30000,
  immediate: true,
  enabled: true,
});

Properties

Prop	Type	Description	Default
onPoll	function	Callback executed when poll interval occurs.
optional.interval	number	What interval the onPoll should be called.	30000
optional.immediate	boolean	If we immediately poll, if false we wait till first interval occurs.	true
optional.enabled	boolean	Is polling enabled.	true

usePrevious

Hook to retrieve a value from the previous render.

Example

import { usePrevious } from '@leafygreen-ui/hooks';

const Example = ({nextValue: number}) => {
  const value = usePrevious(nextValue);

  return <div>{value}</div>;
}

// First render
<Example nextValue={42} />  // will render an empty `div`

// Second render
<Example nextValue={2020} />  // will render "42"

// Third render
<Example nextValue={0} />  // will render "2020"

useIsomorphicLayoutEffect

Drop-in replacement for useLayoutEffect that does not produce warnings during server-side rendering. If your project uses the react-hooks/exhaustive-deps ESLint rule, it's recommended to add useIsomorphicLayoutEffect to the additionalHooks of the rule. Example:

  rules: {
    'react-hooks/exhaustive-deps': [
      'warn',
      {
        additionalHooks: '(useIsomorphicLayoutEffect)'
      }
    ]
  }

useIdAllocator

Generates an SSR-compatible unique id based on a prefix string and an optional idProp parameter.

Example

import { useIdAllocator } from '@leafygreen-ui/hooks';

useIdAllocator({ prefix: 'select-component', id: idProp });

useForwardedRef

Returns a MutableRefObject from the forwarded ref.

Example

import { useForwardedRef } from '@leafygreen-ui/hooks';

const MyComponent = React.forwardRef((props, forwardedRef) => {
  const ref = useForwawrdedRef(forwardedRef, null);
});

Properties

Prop	Type	Description	Default
forwardedRefOrRefs	SettableRef, Array<SettableRef>, null	The forwarded ref
initialValue	T	Initial value of the ref

useDynamicRefs

useDynamicRefs is a hook that allows you to create multiple refs for dynamically created elements. Use the prefix property to create multiple sets of dynamic refs.

Example

import { useDynamicRefs } from '@leafygreen-ui/hooks';

const getRef = useDynamicRefs();
...
return ['a','b','c'].map(x => {
  const divRef = getRef(x)
  return <div ref={divRef}>{x}</div>
})

Properties

Prop	Type	Description	Default
prefix	string	Optional prefix to that genterates a ref name space