Check out my React hooks introduction first, if you’re new to them.
One React hook I sometimes use is useMemo
.
import React, { useMemo } from 'react'
This hook is used to create a memoized value.
This hook is very similar to useCallback, the difference is that
useCallback
returns a memoized callback anduseMemo
returns a memoized value, the result of that function call. The use case is different, too.useCallback
is used for callbacks passed to child components.
Sometimes you have to compute a value, either through a complex calculation or by reaching to the database to make a costly query or to the network.
Using this hook, this operation is done only once, then the value will be stored in the memoized value and the next time you want to reference it, you’ll get it much faster.
Here’s how to use it:
const memoizedValue = useMemo(() => expensiveOperation())
Make sure you add that empty array as a second parameter to useMemo()
, otherwise no memoization will happen at all.
If you need to pass arguments, you also need to pass them in the array:
const memoizedValue = useMemo(() => expensiveOperation(param1, param2), [param1, param2])
If one of the parameters change when you try to access the value, the value of course will be calculated without memoization.
Download my free React Handbook
More react tutorials:
- A React simple app example: fetch GitHub users information via API
- Build a simple counter with React
- VS Code setup for React development
- How to pass props to a child component via React Router
- Create an app with Electron and React
- Tutorial: create a Spreadsheet using React
- The roadmap to learn React
- Learn how to use Redux
- Getting started with JSX
- Styled Components
- Introduction to Redux Saga
- Introduction to React Router
- Introduction to React
- React Components
- The Virtual DOM
- React Events
- The React State
- React Props
- The React Fragment
- The React Context API
- React PropTypes
- React concepts: declarative
- React: How to show a different component on click
- How to loop inside React JSX
- Props vs State in React
- Should you use jQuery or React?
- How much JavaScript you need to know to use React?
- Introduction to Gatsby
- How to reference a DOM element in React
- Unidirectional Data Flow in React
- React Higher Order Components
- React Lifecycle Events
- React Concept: Immutability
- React Concept: Purity
- Introduction to React Hooks
- Introduction to create-react-app
- React Concept: Composition
- React: Presentational vs Container Components
- Code Splitting in React
- Server Side Rendering with React
- How to install React
- CSS in React
- Using SASS in React
- Handling Forms in React
- React StrictMode
- React Portals
- React Render Props
- Testing React components
- How to pass a parameter to event handlers in React
- How to handle errors in React
- How to return multiple elements in JSX
- Conditional rendering in React
- React, how to transfer props to child components
- How to get the value of an input element in React
- How to use the useState React hook
- How to use the useCallback React hook
- How to use the useEffect React hook
- How to use the useMemo React hook
- How to use the useRef React hook
- How to use the useContext React hook
- How to use the useReducer React hook
- How to connect your React app to a backend on the same origin
- The Reach Router Tutorial
- How to use the React Developer Tools
- How to learn React
- How to debug a React application
- How to render HTML in React
- How to fix the `dangerouslySetInnerHTML` did not match error in React
- How I fixed an issue with a React login form state and Browser autofill
- How to configure HTTPS in a React app on localhost
- How to fix the "cannot update a component while rendering a different component" error in React
- Can I use React hooks inside a conditional?
- Using useState with an object: how to update
- How to move around blocks of code with React and Tailwind