Prevent searchbar rerender from useRecentSearches #110
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oshi97
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Apr 14, 2022
| @@ -1,12 +1,18 @@ | |||
| import { useCallback, useEffect, useState } from 'react'; | |||
| import { useCallback, useEffect, useRef, useState } from 'react'; | |||
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I think you're right and we'll need to use something like React.memo to get performance benefits from our useCallback/memo usages
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Oh and I guess I should clarify that I these performance benefits still may or may not be worth it
oshi97
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…ches (#110) SearchBar requires multiple re-renders due to useEffect call in useRecentSearches to setup RecentSearches instance. The changes in this pr ensures a RecentSearches is set on the first render and only re-render if there is an update to `recentSearchesLimit`. Findings when attempt to memoize hooks and testing in SearchBar: Just using `useCallback` and `useMemo` doesn't really avoid unnecessary re-renders in our components. By default, the child components will always re-render if the parent component has triggered a render ([1](https://stackoverflow.com/a/40820657)). But, this can be override with shouldComponentUpdate for class-based component or with `React.memo(SomeComponent)` for functional component. `React.memo` prevents unnecessary re-renders if there's no change in the props (and no state update in the component itself), and we can use useMemo/useCallback to avoid creating new object when passing props to component each time. I attempted to use React.memo on DropdownInput for SearchBar (had to wrap a lot of things in useCallback), but there's a lot of props and state changes from SearchBar interactions that almost certainly would require a re-render of the subcomponents. Clicking in/out of searchbar, typing/submitting/clearing inputs in some way generally trigger some setState functions due to new results and/or make updates to the different contexts that would affect the Dropdown components. Additionally, some advise that components like Dropdown with [child prop shouldn't use React.memo ](facebook/react#14463 (comment) the children prop almost always changes. I believe there may **not** be a lot of benefits for doing useCallback throughout SearchBar to avoid re-renders in its subcomponents. It kind of make the codebase more complicated with the overhead and less readable, unless there's an actual performance bottleneck to address. So I'm a bit hesitant to add more useMemo/useCallback in our hooks and components if we don't need to. J=SLAP-1965 TEST=manual log number of renders in SearchBar before and after useRecentSearch changes. See that SearchBar have less re-renders on initial load.
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SearchBar requires multiple re-renders due to useEffect call in useRecentSearches to setup RecentSearches instance. The changes in this pr ensures a RecentSearches is set on the first render and only re-render if there is an update to
recentSearchesLimit.Findings when attempt to memoize hooks and testing in SearchBar:
Just using
useCallbackanduseMemodoesn't really avoid unnecessary re-renders in our components. By default, the child components will always re-render if the parent component has triggered a render (1). But, this can be override with shouldComponentUpdate for class-based component or withReact.memo(SomeComponent)for functional component.React.memoprevents unnecessary re-renders if there's no change in the props (and no state update in the component itself), and we can use useMemo/useCallback to avoid creating new object when passing props to component each time.I attempted to use React.memo on DropdownInput for SearchBar (had to wrap a lot of things in useCallback), but there's a lot of props and state changes from SearchBar interactions that almost certainly would require a re-render of the subcomponents. Clicking in/out of searchbar, typing/submitting/clearing inputs in some way generally trigger some setState functions due to new results and/or make updates to the different contexts that would affect the Dropdown components. Additionally, some advise that components like Dropdown with child prop shouldn't use React.memo since the children prop almost always changes.
I believe there may not be a lot of benefits for doing useCallback throughout SearchBar to avoid re-renders in its subcomponents. It kind of make the codebase more complicated with the overhead and less readable, unless there's an actual performance bottleneck to address. So I'm a bit hesitant to add more useMemo/useCallback in our hooks and components if we don't need to.
J=SLAP-1965
TEST=manual
log number of renders in SearchBar before and after useRecentSearch changes. See that SearchBar have less re-renders on initial load.