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@arthurgeron/eslint-plugin-react-usememo
Advanced tools
Enforce that all function components are wrapped in `React.memo`, and that all props and deps are wrapped in `useMemo`/`useCallback` so they don’t break memo or cause unecessary expensive re-renders in children (e.g. React Native's FlatLists, useEffect, u
Enforce that all function components are wrapped in React.memo
, and that all props and deps are wrapped in useMemo
/useCallback
so they don’t break memo or cause unecessary expensive re-renders in children (e.g. React Native's FlatLists, useEffect, useMemo).
Why we memo all the things.
React Native's own docs state how it's important to use static or memoized as props for complex children (FlatList on that case), that applies even more broadly when we are talking about custom components (the Components you've created), it might not seem necessary at first but you'll be making a bet that the component in question will never grow to use memo
or those props in hooks (i.e. useEffect, useMemo, useCallback), you'll only notice once your solution starts freezing and dropping frames, that's why using the require-usememo
rule is recommended.
yarn add @arthurgeron/eslint-plugin-react-usememo --dev
or
npm install @arthurgeron/eslint-plugin-react-usememo --save-dev
To enable the plugin add the following to the plugin
property your eslintrc
file:
"plugins": ["@arthurgeron/react-usememo"],
Then enable any rules as you like, example:
"rules": {
"@arthurgeron/react-usememo/require-usememo": [2],
},
require-usememo
RecommendedRequires complex values (objects, arrays, functions, and JSX) that get passed props or referenced as a hook dependency to be wrapped in React.useMemo()
or React.useCallback()
.
Options:
{strict: true}
: Fails even in cases where it is difficult to determine if the value in question is a primitive (string or number) or a complex value (object, array, etc.).function Component() {
const [data, setData] = useState([]);
// This will be redeclared each render
function renderItem({ item }) {
return <Text>item.name</Text>;
}
// Data isn't redeclared each ender but `[]` is
<FlatList renderItem={renderItem} data={data ?? []} />
}
In the previous example there are two issues, a function and a object that will be dynamically redeclared each time the component renders, which will cause FlatList to keep re-rendering even when the input data hasn't changed.
// Has no dynamic dependencies therefore should be static, will be declared only once.
function renderItem({ item }) {
return <Text>item.name</Text>;
}
const EMPTY_ARRAY = [];
function Component() {
const [data, setData] = useState(EMPTY_ARRAY);
<FlatList renderItem={renderItem} data={data ?? EMPTY_ARRAY} />
}
const EMPTY_ARRAY = [];
function Component() {
const [data, setData] = useState(EMPTY_ARRAY);
const [isEditing, setIsEditing] = useState(false);
// Has dynamic dependencies but will only be re-declared when isEditing or the input data changes
const renderItem = useCallback(({ item }) => {
return <Text>{isEditing ? 'item.name' : 'Editing'}</Text>;
}, [isEditing]);
<FlatList renderItem={renderItem} data={data ?? EMPTY_ARRAY} />
}
require-memo
Requires all function components to be wrapped in React.memo()
.
May be useful when used with overrides in your eslint config, I do not recommend enabling this globally, while there's great advantaje in memoing a complex tree of components some smaller/basic components with no children might not need to be memoized.
export default function Component() {
<Text>This is a component</Text>
}
export default memo(function Component() {
<Text>This is a component</Text>
});
require-usememo-children
AdvancedRequires complex values (objects, arrays, functions, and JSX) that get passed as children to be wrapped in React.useMemo()
or React.useCallback()
.
Options:
{strict: true}
: Fails even in cases where it is difficult to determine if the value in question is a primitive (string or number) or a complex value (object, array, etc.).function Component() {
<View>
<>
<OtherComponent />
</>
</View>
}
function Component() {
const children = useMemo(() => (<OtherComponent />), []);
<View>
{children}
</View>
}
FAQs
This plugin enforces the wrapping of complex objects or functions (which might generate unnecessary renders or side-effects) in `useMemo` or `useCallback`. It also allows you to programmatically enforce the wrapping of functional components in `memo`, and
The npm package @arthurgeron/eslint-plugin-react-usememo receives a total of 2,704 weekly downloads. As such, @arthurgeron/eslint-plugin-react-usememo popularity was classified as popular.
We found that @arthurgeron/eslint-plugin-react-usememo demonstrated a healthy version release cadence and project activity because the last version was released less than a year ago. It has 0 open source maintainers collaborating on the project.
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