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https://github.com/theKashey/react-memoize

🧠 React memoization library we all deserve
https://github.com/theKashey/react-memoize

memoize optimization react renderprops

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🧠 React memoization library we all deserve

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README 

        


  
react-memoize  🤯 🧠


  


  memoize

  


  


  

     Build status

  

  

  

   

  

    

  

   

  

  

  

     

  

  

  


  


  
  

  



7kb MobX-level memoization library, which tracks all the arguments you are __really__ depends on.

- It is not so fast, as reselect, but could handle more cases, and works out of the box. 

- It is not so fast, but much faster, than _VDOM tree comparison_ you will face in case of render trashing.  

- It contain 3 types of memoziation to handle all possible cases.



Uses [memoize-state](https://github.com/theKashey/memoize-state) underneath, providing the same magic for `get` as [immer](https://github.com/mweststrate/immer) provided to `set`. 



Works fine in all browsers including IE11.



__Just write code as you want. It it will be properly memoized__.



This is declarative component memoization for React! Based on [Dan Abramov's tweet](https://twitter.com/dan_abramov/status/965378278461755392)

Could change the way you did `componentWillReceiveProps`, could replace `getDerivedStateFromProps`, could make things better.



> IE11+, React 15 and React 16.3 compatible.



- [Memoize](#memoize) - to create declarative memoized selection.

- [MemoizedFlow](#flow) - to create declarative memoized flow.

- [MemoizeContext](#memoizecontext) - to create memoized selector from context(or any Consumer).

- [MemoizedRender](#memoizedrender) - to create a render, memoized by a value provided. 



Memoize, MemoizedFlow, MemoizeContext accepts one or more functions to select or transform incoming data, and provide result to a function-as-child.



MemoizedRender is memoizing the function-as-child itself.



> What is the difference between React-memoize and React.memo? Memo is a "PureComponent", Memoize is more about 

accurate memoization based on the real props consumption.

React-memoize is about "calculation" memoization



### Memoize



```js

 import Memoize from 'react-memoize';

 

  heavyComputation(state[prop1])} // Memoize tracks WHAT you are doing 

   pure // Memoize will be a pure component itself

  >

  { result => {result}}

  

```

There is only __one prop__ - `compute`, all others will be passed inside.

Memoize get `compute` function, add passes all the other props to it, streaming result to the render prop.



If `pure` prop is set ReactMemoize wil behave as PureComponent, and not update children when could not. 



## Flow

`getDerivedStateFromProps` gives you ability to derive a new state from props, while `componentDidUpdate` enables you to react 

to the state changes.



__MemoizedFlow__ is `getDerivedStateFromState`. Following example react to the state changes, allowing 

to change ordering of rows and applies a pagination.



"The Flow" is safe and performant way to form something from something, and rebuilt then the time calls.

```js

import {MemoizedFlow} from 'react-memoize';



class SortablePageableTable extends Component {

    state = {

    page:0,

    perPage:10,

    filter: I => I

    };

    

    onSortChange = (order) => this.setState(order)

    onPageChange = page => this.setState(page);

    

    render () {

    return (

           ({rows: list.filter(filter)}),

            // will react on rows(from step1) change or order

            ({rows, order}) => ({rows: list.slice().sort(order)}), // !! clone array before sort

            // will react on rows and pagination changes

            ({rows, page, perPage}) => ({rows: list.slice(page*perPage, (page+1)*perPage)}),

            // will react on something else, not related

            ({rain, bows}) => ({rainbows: rain+bows, rain: null, bows: null })

            ]}

          >

            {output => }

          

    }

}



```

First step is getting `input`, and each following is reading from a value provided before, spreading

own result over it. Until the last step will be reached, and output will be provided to render prop.



Each step is memoized, as usual, and will always reuse value from the steps before. 



### MemoizeContext

React memoize also provides component to __select__ and __memoize__ data from React16 context, or any other component 

which will pass some values into renderProp.



```js

import {MemoizeContext} from 'react-memoize';



    

      {values => }

    



``` 

`consumer` could be any "context"-compatible Component - React.context, create-react-context, unstated, react-copy-write.

All the additional props will be passed down to consumer. 



It is better to explain using example.

```js

 />



// will result



{ contextValues => ...}



```



This is like Redux without dispatching. State in context, selector aka mapStateToProps, and magic memoization in between.



__See it in action ->__ https://codesandbox.io/s/xjz5y3wzrz 🛠



# MemoizedRender

MemoizedRender is mostly usable with Context API

```js

import {MemoizedRender} from 'react-memoize';



    

      {values => }

    



```

Or, the better example (from [react-copy-write](https://github.com/aweary/react-copy-write#consuming-state))

```js

const UserAvatar = ({ id }) => (

  

    {state => (

      


        

      


    )}

  

);

```

While `react-copy-write` declares that _ The problem with this is that whenever any value in state changes, UserAvatar will be re-rendered, even though it's only using a single property from a single, nested object._

This example will work, as long MemoizedRender will track used keys, and perform update only when necessary.



It is also possible to provide `value` as a prop

```js



  {values => }



```



MemoizedRender __memoizes "render" as a whole__. This is __absolute pure component__. Be carefull. Might be not 100% compatible with async rendering

if you pass values you were provided down the tree, as long __async accessed keys are not tracked__.

Thus - MemoizedRender may not react to changes in them.



## About



React-memoize uses [memoize-state](https://github.com/theKashey/memoize-state) underneath to perform __MobX__ like memozation

and achive the maximal minimal level of memoization cache misses. Sounds a bit strange, but this mean - react-memoize will try to preserve the current `state` at all costs. From 10% to 50% "more" in comparison.



> In all the cases only ONE! result is memoized. The goal of the component is to cut off updates.



For example:



- recomputation will be made only when stateSubKey is changed

```js

  soSomethingWith(state.stateSubKey)}

  >

  { result => ....}

  

``` 

- recomputation will be made only when used prop is changed

```js

  soSomethingWith(usedProp)}

  >

  { result => ....}

  

``` 

- recomputation will be make only when item count changes, value of any item or text of items __passed__ thought the filter.

```js

  list.filter(item => item.value).map(item => item.text)}

  >

  { result => ....}

  

``` 



The same magic as in [beautiful-react-redux](https://github.com/theKashey/beautiful-react-redux), kudos to `memoize-state` library.



PS: For systems without Proxy support memoize will use [memoize-one](https://github.com/alexreardon/memoize-one)



# Licence

 MIT