Hooks

!npm (scoped)

Installation

$3

``shell
pnpm add @leafygreen-ui/hooks
`

$3

`shell
yarn add @leafygreen-ui/hooks
`

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`shell
npm install @leafygreen-ui/hooks
`

useEventListener

Hook to create and remove eventListeners

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

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

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| 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.

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

useEscapeKey(handleEscapeCallback);
`

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| 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

$3

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

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

$3

| 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

$3

`js
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.

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

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

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| 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.

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

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

return

// First render
// will render an empty div

// Second render
// will render "42"

// Third render
// 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:

`js
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.

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

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

useForwardedRef

Returns a MutableRefObject from the forwarded ref.

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

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

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| Prop | Type | Description | Default |
| -------------------- | ------------------------------------------- | ------------------------ | ------- |
| forwardedRefOrRefs | SettableRef, Array, 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.

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

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

`

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