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# useMemoOne
[`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)
[![Build Status](https://travis-ci.org/alexreardon/use-memo-one.svg?branch=master)](https://travis-ci.org/alexreardon/use-memo-one)
[![npm](https://img.shields.io/npm/v/use-memo-one.svg)](https://www.npmjs.com/package/use-memo-one)
[![dependencies](https://david-dm.org/alexreardon/use-memo-one.svg)](https://david-dm.org/alexreardon/use-memo-one)
[![min](https://img.shields.io/bundlephobia/min/use-memo-one.svg)](https://bundlephobia.com/result?p=use-memo-one)
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## Background
`useMemo` and `useCallback` cache the most recent result. However, this cache can be destroyed by `React` when it wants to:
> 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)
`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.
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.
## Install
```bash
# npm
npm install use-memo-one --save
# yarn
yarn add use-memo-one
```
## Usage
```js
import { useMemoOne, useCallbackOne } from 'use-memo-one';
function App(props) {
const { name, age } = props;
const value = useMemoOne(() => ({ hello: name }), [name]);
const getAge = useCallbackOne(() => age, [age]);
// ...
}
```
### Aliased imports
You can use this `import` style drop in replacement for `useMemo` and `useCallback`
This style also plays very well with [`eslint-plugin-react-hooks`](https://www.npmjs.com/package/eslint-plugin-react-hooks).
```js
import { useMemo, useCallback } from 'use-memo-one';
```
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`
```js
import { useMemo, useCallback } from 'react';
// ❌ naming clash
import { useMemo, useCallback } from 'use-memo-one';
```
## API
See [`useMemo`](https://reactjs.org/docs/hooks-reference.html#usememo) and [`useCallback`](https://reactjs.org/docs/hooks-reference.html#usecallback)
## Linting
`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:
```js
import { useMemo, useCallback } from 'use-memo-one';
// Or your can alias it yourself
import {
useMemoOne as useMemo,
useCallbackOne as useCallback,
} from 'use-memo-one';
function App() {
const [isActive] = useState(false);
const onClick = useCallback(() => {
console.log('isActive', isActive);
// the input array will now be correctly checked by eslint-plugin-react-hooks
}, [isActive]);
}
```
## [`eslint`](https://eslint.org/) rules
Here are some `eslint` rules you are welcome to use
```js
module.exports = {
rules: {
// ...other rules
'no-restricted-imports': [
'error',
{
// If you want to force an application to always use useMemoOne
paths: [
{
name: 'react',
importNames: ['useMemo', 'useCallback'],
message:
'`useMemo` and `useCallback` are subject to cache busting. Please use `useMemoOne`',
},
// If you want to force use of the aliased imports from useMemoOne
{
name: 'use-memo-one',
importNames: ['useMemoOne', 'useCallbackOne'],
message:
'use-memo-one exports `useMemo` and `useCallback` which work nicer with `eslint-plugin-react-hooks`',
},
],
},
],
},
};
```