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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 | 1x 1x 1x 1x 1x 2x 2x 2x 2x 2x 1x 1x 1x 1x 3x 1x 1x 1x 2x | import React from 'react' export default function create(fn) { let state = { listeners: [], current: fn( merge => { Eif (typeof merge === 'function') merge = merge(state.current) state.current = Object.assign({}, state.current, merge) state.listeners.forEach(listener => listener(state.current)) }, () => state.current ), } return [ // useStore (selector, dependencies) => { let selected = selector ? selector(state.current) : state.current // Using functional initial b/c selected itself could be a function const [slice, set] = React.useState(() => selected) const sliceRef = React.useRef() React.useEffect(() => void (sliceRef.current = slice), [slice]) React.useEffect(() => { const ping = () => { // Get fresh selected state let selected = selector ? selector(state.current) : state.current // If state is not equal from the get go and not an atomic then shallow equal it Eif ( sliceRef.current !== selected && typeof selected === 'object' && !Array.isArray(selected) ) { selected = Object.entries(selected).reduce( (acc, [key, value]) => sliceRef.current[key] !== value ? Object.assign({}, acc, { [key]: value }) : acc, sliceRef.current ) } // Refresh local slice, functional initial b/c selected itself could be a function Eif (sliceRef.current !== selected) set(() => selected) } state.listeners.push(ping) return () => (state.listeners = state.listeners.filter(i => i !== ping)) }, dependencies || [selector]) // Returning the selected state slice return selected }, { subscribe: fn => { state.listeners.push(fn) return () => (state.listeners = state.listeners.filter(i => i !== fn)) }, getState: () => state.current, destroy: () => ((state.listeners = []), (state.current = {})), }, ] } |