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# useMemoOne |
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[`useMemo`](https://reactjs.org/docs/hooks-reference.html#usememo) and [`useCallback`](https://reactjs.org/docs/hooks-reference.html#usecallback) with a stable cache (semantic guarantee) |
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[![Build Status](https://travis-ci.org/alexreardon/use-memo-one.svg?branch=master)](https://travis-ci.org/alexreardon/use-memo-one) |
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[![npm](https://img.shields.io/npm/v/use-memo-one.svg)](https://www.npmjs.com/package/use-memo-one) |
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[![dependencies](https://david-dm.org/alexreardon/use-memo-one.svg)](https://david-dm.org/alexreardon/use-memo-one) |
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[![min](https://img.shields.io/bundlephobia/min/use-memo-one.svg)](https://bundlephobia.com/result?p=use-memo-one) |
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[![minzip](https://img.shields.io/bundlephobia/minzip/use-memo-one.svg)](https://bundlephobia.com/result?p=use-memo-one) |
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## Background |
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`useMemo` and `useCallback` cache the most recent result. However, this cache can be destroyed by `React` when it wants to: |
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> You may rely on useMemo as a performance optimization, **not as a semantic guarantee**. In the future, **React may choose to “forget” some previously memoized values** and recalculate them on next render, e.g. to free memory for offscreen components. Write your code so that it still works without useMemo — and then add it to optimize performance. [- React docs](https://reactjs.org/docs/hooks-reference.html#usememo) |
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`useMemoOne` and `useCallbackOne` are `concurrent mode` safe alternatives to `useMemo` and `useCallback` **that do provide semantic guarantee**. What this means is that you will always get the same reference for a memoized value so long as there is no input change. |
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Using `useMemoOne` and `useCallbackOne` will consume more memory than `useMemo` and `useCallback` in order to provide a stable cache. `React` can release the cache of `useMemo` and `useCallback`, but `useMemoOne` will not release the cache until it is garbage collected. |
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## Install |
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```bash |
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# npm |
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npm install use-memo-one --save |
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# yarn |
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yarn add use-memo-one |
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``` |
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## Usage |
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```js |
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import { useMemoOne, useCallbackOne } from 'use-memo-one'; |
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function App(props) { |
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const { name, age } = props; |
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const value = useMemoOne(() => ({ hello: name }), [name]); |
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const getAge = useCallbackOne(() => age, [age]); |
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// ... |
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} |
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``` |
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### Aliased imports |
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You can use this `import` style drop in replacement for `useMemo` and `useCallback` |
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This style also plays very well with [`eslint-plugin-react-hooks`](https://www.npmjs.com/package/eslint-plugin-react-hooks). |
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```js |
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import { useMemo, useCallback } from 'use-memo-one'; |
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``` |
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⚠️ The aliased exports `useMemo` and `useCallback` will only work if you use _only_ `use-memo-one` and will clash if you also use `useMemo` or `useCallback` from `react` |
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```js |
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import { useMemo, useCallback } from 'react'; |
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// ❌ naming clash |
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import { useMemo, useCallback } from 'use-memo-one'; |
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``` |
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## API |
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See [`useMemo`](https://reactjs.org/docs/hooks-reference.html#usememo) and [`useCallback`](https://reactjs.org/docs/hooks-reference.html#usecallback) |
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## Linting |
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`useMemo` and `useCallback` have fantastic linting rules with auto fixing in the [`eslint-plugin-react-hooks`](https://www.npmjs.com/package/eslint-plugin-react-hooks) package. In order to take advantage of these with `useMemoOne` and `useCallbackOne`, structure your import like this: |
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```js |
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import { useMemo, useCallback } from 'use-memo-one'; |
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// Or your can alias it yourself |
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import { |
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useMemoOne as useMemo, |
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useCallbackOne as useCallback, |
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} from 'use-memo-one'; |
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function App() { |
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const [isActive] = useState(false); |
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const onClick = useCallback(() => { |
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console.log('isActive', isActive); |
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// the input array will now be correctly checked by eslint-plugin-react-hooks |
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}, [isActive]); |
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} |
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``` |
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## [`eslint`](https://eslint.org/) rules |
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Here are some `eslint` rules you are welcome to use |
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```js |
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module.exports = { |
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rules: { |
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// ...other rules |
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'no-restricted-imports': [ |
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'error', |
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{ |
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// If you want to force an application to always use useMemoOne |
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paths: [ |
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{ |
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name: 'react', |
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importNames: ['useMemo', 'useCallback'], |
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message: |
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'`useMemo` and `useCallback` are subject to cache busting. Please use `useMemoOne`', |
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}, |
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// If you want to force use of the aliased imports from useMemoOne |
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{ |
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name: 'use-memo-one', |
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importNames: ['useMemoOne', 'useCallbackOne'], |
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message: |
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'use-memo-one exports `useMemo` and `useCallback` which work nicer with `eslint-plugin-react-hooks`', |
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}, |
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], |
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}, |
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], |
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}, |
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}; |
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```
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