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Initial implementation of useLazyState BREAKING CHANGE: Initial implementation
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -1 +1,76 @@ | ||
| export const myPackage = (taco = ''): string => `${taco} from my package`; | ||
| import { useEffect, useRef, useState } from 'react'; | ||
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| export type UseLazyStateSetter<T> = (prev: T) => T; | ||
| export type UseLazyState<T> = { | ||
| _stateRef: any; | ||
| setState: (action: T | UseLazyStateSetter<T>) => void; | ||
| useState: <D = T>(getter?: (state: T) => D) => D; | ||
| }; | ||
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| type Subscriber = { | ||
| id: number; | ||
| triggerUpdate: () => void; | ||
| }; | ||
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| export const useLazyState = <T>(initialState: T): UseLazyState<T> => { | ||
| const subscriberId = useRef<number>(0); | ||
| const ref = useRef<T>(initialState); | ||
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| const subscribers = useRef<Subscriber[]>([]); | ||
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| const setState: UseLazyState<T>['setState'] = action => { | ||
| if (typeof action === 'function') { | ||
| ref.current = (action as UseLazyStateSetter<T>)(ref.current); | ||
| } else { | ||
| const state = action; | ||
| ref.current = state; | ||
| } | ||
| for (const subscriber of subscribers.current) { | ||
| subscriber.triggerUpdate(); | ||
| } | ||
| }; | ||
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| const _useState = function _useState<D = T>(_getter?: (state: T) => D): D { | ||
| const getter = | ||
| typeof _getter === 'undefined' ? (state: T): T => state : _getter; | ||
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| if (typeof getter !== 'function') | ||
| throw new Error('Getter must be a function'); | ||
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| const innerInitialState = getter(initialState); | ||
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| // stateRef to maintain a reference to an object that triggerUpdate could point to | ||
| const currentStateRef = useRef<any>(innerInitialState); | ||
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| // useState to trigger react rendering when it is updated | ||
| const [currentState, setCurrentState] = useState(innerInitialState); | ||
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| // Subscribe the hook to get global updates when changes happen in the state | ||
| useEffect(() => { | ||
| const id = subscriberId.current; | ||
| subscribers.current.push({ | ||
| id, | ||
| triggerUpdate: () => { | ||
| const newState = getter(ref.current); | ||
| const currentState = currentStateRef.current; | ||
| if (currentState && newState === currentState) return; // no need to update state | ||
| // update state | ||
| currentStateRef.current = newState; | ||
| setCurrentState(newState); | ||
| }, | ||
| }); | ||
| subscriberId.current = subscriberId.current + 1; | ||
| return () => { | ||
| subscribers.current = subscribers.current.filter(s => s.id !== id); | ||
| }; | ||
| }, []); | ||
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| return currentState as D; | ||
| }; | ||
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| return { | ||
| _stateRef: ref, | ||
| setState, | ||
| useState: _useState, | ||
| }; | ||
| }; |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -1,13 +1,7 @@ | ||
| import { myPackage } from '../src'; | ||
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| describe('index', () => { | ||
| describe('myPackage', () => { | ||
| it('should return a string containing the message', () => { | ||
| const message = 'Hello'; | ||
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| const result = myPackage(message); | ||
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| expect(result).toMatch(message); | ||
| describe('useLazyState', () => { | ||
| it('true === true', () => { | ||
| expect(true).toBe(true); | ||
| }); | ||
| }); | ||
| }); |