39 lines
1.2 KiB
JavaScript
39 lines
1.2 KiB
JavaScript
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// Avoid re-renders by caching the most recent value of an array
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// or an object, using an approach similar to https://github.com/reactjs/reselect.
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// This avoids the issue where Svelte may keep re-rendering because it doesn't
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// know if an object/array has changed or not.
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import isEqual from 'lodash/isEqual'
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if (process.browser && process.env.NODE_ENV !== 'production') {
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window.reselectStats = {}
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}
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export function reselect (store, outputKey, inputKey) {
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let prevValue
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let nextValue
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let count = 0
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let countKey = `${outputKey}_reselectCount`
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store.compute(countKey, [inputKey], input => {
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if (process.browser && process.env.NODE_ENV !== 'production') {
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window.reselectStats[inputKey] = window.reselectStats[inputKey] || {numInputChanges: 0, numOutputChanges: 0}
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window.reselectStats[inputKey].numInputChanges++
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}
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if (!isEqual(prevValue, input)) {
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nextValue = input
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count++
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}
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return count
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})
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store.compute(outputKey, [countKey], () => {
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if (process.browser && process.env.NODE_ENV !== 'production') {
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window.reselectStats[inputKey].numOutputChanges++
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}
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prevValue = nextValue
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nextValue = null
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return prevValue
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})
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}
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