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
npm install @arthurgeron/eslint-plugin-react-usememoThis 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 that all props and dependencies are wrapped in useMemo/useCallback.
The objective is to ensure that your application's component tree and/or expensive lifecycles (such as React Native's FlatLists, useEffect, useMemo, etc.) only re-calculate or render again when absolutely necessary. By controlling expensive expressions, you can achieve optimal scalability and performance for your application.
_Note:_ Use of memoization everywhere is not advised, as everything comes with a cost. Overusing memoization might slow down your application instead of speeding it up.
> For more details, please refer to React's documentation on hooks, re-rendering and memoization.
1. Variables or expressions that return non-primitive objects or functions passed as props to other components.
_Incorrect_
``js
function Component({ incomingData }) {
const complexData = {
...incomingData,
checked: true,
}; // generated each render, breaks hooks shallow comparison
return
}
`
_Correct_
`js
function Component({ incomingData }) {
const complexData = useMemo(
() => ({
...incomingData,
checked: true,
}),
[incomingData],
); // generated only when incomingData changes
return
}
`
2. Variables or expressions that return non-primitive objects returned from custom hooks.
_Incorrect_
`js
function useMyData({ incomingData }) {
const parsedData = parseData(incomingData); // generated each render
return parsedData; // Will result in loops passed as a dependency in other hooks(e.g. useMemo, useCallback, useEffect).
}
`
_Correct_
`js
function useMyData({ incomingData }) {
const parsedData = useMemo(() => parseData(incomingData), [incomingData]); // generated only when incomingData changes
return parsedData; // Won't generate loops if used as a dependency in hooks.
}
`
- When the resulting value (expression or variable) is primitive (string, number, boolean).
_Incorrect_
`js
function Component() {
const width = useMemo(() => someValue * 10, []); // results in integer, wouldn't break hooks' shallow comparison; Memoizing this would only reduce performance
return
}
`
_Correct_
`js
function Component() {
const width = someValue * 10;
return
}
`
- If you're passing props to a native component of the framework (e.g. Div, Touchable, etc), except in some instances in react-native (e.g. FlatList).
_Incorrect_
`js
function Component() {
const onClick = useCallback(() => {}, []);
return
; _Correct_
js
function Component() {
const onClick = () => {}; return
;
}
`- Values that can be a global/context outside the react Context.
_Incorrect_
js
function Component() {
const breakpoints = [100]; return
}
` _Correct_
js
const breakpoints = [100]; function Component() {
return
}
`Installation
Install it with yarn:
yarn add @arthurgeron/eslint-plugin-react-usememo --dev
or npm:
npm install @arthurgeron/eslint-plugin-react-usememo --save-dev
Compatibility
This plugin targets ESLint v9+ (flat config). ESLint v8 is no longer supported. The package exposes named exports only.
$3
#### Option 1: Use the plugin directly
js
import { flatConfig } from "@arthurgeron/eslint-plugin-react-usememo";export default [
{
files: ["/.js", "/.jsx", "/.ts", "/.tsx"],
languageOptions: {
ecmaVersion: 2020,
sourceType: "module",
parserOptions: {
ecmaFeatures: {
jsx: true,
},
},
},
plugins: {
"@arthurgeron/react-usememo": flatConfig,
},
rules: {
"@arthurgeron/react-usememo/require-usememo": "error",
"@arthurgeron/react-usememo/require-memo": "error",
"@arthurgeron/react-usememo/require-usememo-children": "error",
},
},
];
`#### Option 2: Use the recommended config
js
import { flatConfig } from "@arthurgeron/eslint-plugin-react-usememo";export default [
flatConfig.configs.recommended,
];
`#### Option 3: CommonJS syntax
js
const { flatConfig } = require("@arthurgeron/eslint-plugin-react-usememo");module.exports = [
{
plugins: {
"@arthurgeron/react-usememo": flatConfig,
},
rules: {
"@arthurgeron/react-usememo/require-usememo": "error",
"@arthurgeron/react-usememo/require-memo": "error",
"@arthurgeron/react-usememo/require-usememo-children": "error",
},
},
];
`For migration guidance, please refer to our ESLint v9 Migration Guide.
Examples
For a working example of ESLint v9 (flat config), please check the examples directory.
Rule #1:
_(recommended)_This rule requires complex values (objects, arrays, functions, and JSX) that get passed props or referenced as a hook dependency to be wrapped in useMemo() or useCallback().
One of the great features of this rule is its amazing autofix functionality. It intelligently wraps necessary components with useMemo() or useCallback(), making your code more efficient and saving you valuable time.
For detailed examples, options available for this rule, and information about the autofix functionality, please refer to our rules documentation.
Rule #2:
require-memoThis rule requires all function components to be wrapped in
.For detailed examples and usage of this rule, please refer to our rules documentation
Rule #3:
require-usememo-childrenThis rule requires complex values (objects, arrays, functions, and JSX) that get passed as children to be wrapped in
or useCallback().For detailed examples and options available for this rule, please refer to our rules documentation.
Conclusion
By efficiently using
useMemo, useCallback, and React.memo()`, we can optimize our React and React Native applications. It allows us to control the re-calculation and re-rendering of components, offering better scalability and performance.