Create Context Helper

Create react context especially atomic context without painless.

With Atomic Context your component will only re-render based on atomic value changes but not the whole value you provide in a common pattern. It's simple to use and more powerful. check

Install

$ yarn add create-context-helper
# or
$ npm i create-context-helper

Usage

This library provide createContextHelper to create a common pattern Context And createAtomicContextHelper to create atomic Context.

createContextHelper

import { createContextHelper } from 'create-context-helper'

const [FooBarProvider, useFooBar] = createContextHelper<{
  foo: string
  bar: string
}>('FooBar', {
  foo: '',
  bar: '',
})

const App = () => {
  return (
    <FooBarProvider foo={'hello'} bar={'world'}>
      <Comp />
    </FooBarProvider>
  )
}

const Comp = () => {
  const { foo, bar } = useFoo()
  return (
    <div>
      {foo} {bar} // hello world
    </div>
  )
}

createAtomicContextHelper

import { createAtomicContextHelper } from 'create-context-helper'

const [FooBarProvider, useFooBar] = createAtomicContextHelper<{
  foo: string
  bar: string
}>('FooBar', {
  foo: '',
  bar: '',
})

const App = () => {
  return (
    <FooBarProvider foo={'hello'} bar={'world'}>
      <Comp />
    </FooBarProvider>
  )
}

const Comp = () => {
  const { foo } = useFooBar(['foo'])
  return <div>{foo} // hello</div>
}

Simple as createContextHelper, but more powerful. Your context now becomes atomic which means now taking useFoo(['foo']) for value foo, the component will only change when foo changes.

createAtomicContextHelper will generate a provider tree for you like this

<FooBarProvider>
  <FooBar.foo.Provider>
    <FooBar.bar.Provider>
      <Comp />
    </FooBar.bar.Provider>
  </FooBar.foo.Provider>
</FooBarProvider>

And with selector ['foo'] in hook useFooBar, the FooBarProvider will only collects FooBar.foo.Context for you. which means <Comp /> only re-render when foo changes.

Reference

export const createContextHelper = <
  ContextType,
  ProviderProps extends Partial<ContextType> = Partial<ContextType>,
>(
  // prefix for provider displayName
  prefix: string,
  // context defaultValue
  defaultValue: ContextType,
): [
  // provider
  React.FC<ProviderProps>,
  // use hook
  () => ContextType,
  // context
  React.Context<ContextType>
]

export const createAtomicContextHelper = <
  ContextType extends { [s: string]: any },
  ProviderProps extends Partial<ContextType> = Partial<ContextType>,
  K extends keyof ContextType = keyof ContextType,
>(
  // prefix for provider displayName
  prefix: string,
  // context defaultValue
  defaultValue: ContextType,
): [
  // provider
  React.FC<ProviderProps>,
  // use hook
  <T extends K[] = K[]>(selector?: T) => Pick<ContextType, T[number]>,
  // contextMap
  Record<keyof ContextType, React.Context<ContextType[string]>>,
]

Limitation

There is no magic in createAtomicContextHelper, It only separates shallow values in the original Provider into smaller providers. Inside createAtomicContextHelper, it calls useContext conditional depends on selector. So dynamic selector is not allowed. if don't, it will cause a serious render problem(createAtomicContextHelper handles this scenario by using the first selector).

License

MIT