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Ultimate ReactJS Cheatsheet for Front-End Developers in 2022

Coding Cheat Sheets for programmers are useful to have besides. These often help us to remember various code syntax, and shortcuts and see different concepts visually. Now, ReactJS is one of the most popular frameworks for front-end development, and as it is a huge programming framework, you can’t always memorize every bit of it (especially if you’re new to this field). For that reason, we have carefully created an Ultimate Reactjs Cheatsheet for you to have a smooth experience while coding with Reactjs.

What is ReactJS?

JavaScript or JS is a common term amongst web developers. It is a scripting language that is highly used to build UI elements that make a website more assertive, responsive, and interactive. But building a functional reactive UI element that gains an appreciable user experience may seem very complex and time-consuming. That’s where Reactjs enters the game.

React is a front-end JavaScript library that helps us create UI components without hassle. These components are also reusable so sometimes if we are lucky enough we may not need to write code at all. It is a UI Component Library that only works in our application’s view layer.

ReactJS Cheatsheet

Here, you will find the ultimate Reactjs cheatsheet for 2022.

reactjs cheatsheeet for front-end developers

New Features

Automatic Batching

// Before: only React events were batched.
setTimeout(() => {
  setCount(c => c + 1);
  setFlag(f => !f);
  // React will render twice, once for each state update (no batching)
}, 1000);

// After: updates inside of timeouts, promises,
// native event handlers or any other event are batched.
setTimeout(() => {
  setCount(c => c + 1);
  setFlag(f => !f);
  // React will only re-render once at the end (that's batching!)
}, 1000);

Details

Returning Multiple Elements

You can return multiple elements as arrays or fragments.

Arrays

render () {
  // Don't forget the keys!
  return [
    <li key="A">First item</li>,
    <li key="B">Second item</li>
  ]
}

Fragments

render () {
  // Fragments don't require keys!
  return (
    <Fragment>
      <li>First item</li>
      <li>Second item</li>
    </Fragment>
  )
}

Returning Strings

render() {
  return 'Look ma, no spans!';
}

You can return just a string.

Fragments and Strings

Errors

class MyComponent extends Component {
  ···
  componentDidCatch (error, info) {
    this.setState({ error })
  }
}

Catch errors via componentDidCatch. (React 16+)

Details

Portals

render () {
  return React.createPortal(
    this.props.children,
    document.getElementById('menu')
  )
}

This renders this.props.children into any location in the DOM.

Details

Hydration

const el = document.getElementById('app');
ReactDOM.hydrate(<App />, el);

Use ReactDOM.hydrate instead of using ReactDOM.render if you’re rendering over the output of ReactDOMServer.

Details

Hooks

State Hook

import React, { useState } from 'react';

function Example() {
  // Declare a new state variable, which we'll call "count"
  const [count, setCount] = useState(0);

  return (
    <div>
      <p>You clicked {count} times</p>
      <button onClick={() => setCount(count + 1)}>Click me</button>
    </div>
  );
}

Details

Declaring Multiple State Variables

function ExampleWithManyStates() {
  // Declare multiple state variables!
  const [age, setAge] = useState(42);
  const [fruit, setFruit] = useState('banana');
  const [todos, setTodos] = useState([{ text: 'Learn Hooks' }]);
  // ...
}

Effect Hook

import React, { useState, useEffect } from 'react';

function Example() {
  const [count, setCount] = useState(0);

  // Similar to componentDidMount and componentDidUpdate:
  useEffect(() => {
    // Update the document title using the browser API
    document.title = `You clicked ${count} times`;
  }, [count]);

  return (
    <div>
      <p>You clicked {count} times</p>
      <button onClick={() => setCount(count + 1)}>Click me</button>
    </div>
  );
}

Details

Building Your Hooks

Define FriendStatus

import React, { useState, useEffect } from 'react';

function FriendStatus(props) {
  const [isOnline, setIsOnline] = useState(null);

  useEffect(() => {
    function handleStatusChange(status) {
      setIsOnline(status.isOnline);
    }

    ChatAPI.subscribeToFriendStatus(props.friend.id, handleStatusChange);
    return () => {
      ChatAPI.unsubscribeFromFriendStatus(props.friend.id, handleStatusChange);
    };
  }, [props.friend.id]);

  if (isOnline === null) {
    return 'Loading...';
  }
  return isOnline ? 'Online' : 'Offline';
}

Use FriendStatus

function FriendStatus(props) {
  const isOnline = useFriendStatus(props.friend.id);

  if (isOnline === null) {
    return 'Loading...';
  }
  return isOnline ? 'Online' : 'Offline';
}

Details

Components

Components

import React from 'react';
import ReactDOM from 'react-dom';
class Hello extends React.Component {
  render() {
    return <div className="message-box">Hello {this.props.name}</div>;
  }
}
const el = document.body;
ReactDOM.render(<Hello name="John" />, el);

Use the React.js jsfiddle or the unofficial jsbin to start hacking.

Import Multiple Exports

import React, { Component } from 'react';
import ReactDOM from 'react-dom';
class Hello extends Component {
  ...
}

Properties

<video fullscreen="{true}" autoplay="{false}" />

render () {
  this.props.fullscreen
  const { fullscreen, autoplay } = this.props
  ···
}

Use this.props to access properties passed to the component.

Details

States

constructor(props) {
  super(props)
  this.state = { username: undefined }
}
this.setState({ username: 'rstacruz' });

render () {
  this.state.username
  const { username } = this.state
  ···
}

Use states (this.state) to manage dynamic data.

With Babel, you can use proposal-class-fields and get rid of constructor

class Hello extends Component {
  state = { username: undefined };
  ...
}

Details

Nesting

class Info extends Component {
  render() {
    const { avatar, username } = this.props;

    return (
      <div>
        <UserAvatar src={avatar} />
        <UserProfile username={username} />
      </div>
    );
  }
}

Now, fragments can be used to return multiple children without adding extra wrapping nodes to the DOM.

import React, { Component, Fragment } from 'react';

class Info extends Component {
  render() {
    const { avatar, username } = this.props;

    return (
      <Fragment>
        <UserAvatar src={avatar} />
        <UserProfile username={username} />
      </Fragment>
    );
  }
}

Details

Children

<AlertBox>
  <h1>You have pending notifications</h1>
</AlertBox>
class AlertBox extends Component {
  render() {
    return <div className="alert-box">{this.props.children}</div>;
  }
}

Children are passed as the children property.

Defaults

Setting Default Props

Hello.defaultProps = {
  color: 'blue',
};

Details

Setting Default State

class Hello extends Component {
  constructor(props) {
    super(props);
    this.state = { visible: true };
  }
}

Set the default state in the constructor().

And without constructor using Babel with proposal-class-fields.

class Hello extends Component {
  state = { visible: true };
}

Details

Other Components

Functional components

function MyComponent({ name }) {
  return <div className="message-box">Hello {name}</div>;
}

Functional components have no state. Also, their props are passed as the first parameter to a function.

Function and Class Components

Pure components

import React, {PureComponent} from 'react'

class MessageBox extends PureComponent {
  ···
}

Performance-optimized version of React.Component. Doesn’t rerender if props/state hasn’t changed.

Pure Components

Component API

this.forceUpdate();
this.setState({ ... })
this.setState(state => { ... })
this.state;
this.props;

These methods and properties are available for Component instances.

Details

DOM Nodes

References

class MyComponent extends Component {
  render() {
    return (
      <div>
        <input ref={(el) => (this.input = el)} />
      </div>
    );
  }

  componentDidMount() {
    this.input.focus();
  }
}

Allows access to DOM nodes.

Details

DOM Events

class MyComponent extends Component {
  render() {
    <input type="text" value={this.state.value} onChange={(event) => this.onChange(event)} />;
  }

  onChange(event) {
    this.setState({ value: event.target.value });
  }
}

Pass functions to attributes like onChange.

Details

Other Features

Transferring Props

<VideoPlayer src="video.mp4" />
class VideoPlayer extends Component {
  render() {
    return <VideoEmbed {...this.props} />;
  }
}

Propagates src="..." down to the sub-component.

Details

Top-level API

React.createClass({ ... })
React.isValidElement(c)
ReactDOM.render(<Component />, domnode, [callback]);
ReactDOM.unmountComponentAtNode(domnode);
ReactDOMServer.renderToString(<Component />);
ReactDOMServer.renderToStaticMarkup(<Component />);

There are more, but these are the most common.

Details

JSX patterns

Style Shorthand

const style = { height: 10 };
return <div style={style}></div>;
return <div style={{ margin: 0, padding: 0 }}></div>;

Inline Styles

Inner HTML

function markdownify() {
  return '<p>...</p>';
}
<div dangerouslySetInnerHTML={{ __html: markdownify() }} />;

Details

Lists

class TodoList extends Component {
  render() {
    const { items } = this.props;

    return (
      <ul>
        {items.map((item) => (
          <TodoItem item={item} key={item.key} />
        ))}
      </ul>
    );
  }
}

Always supply a key property.

Conditionals

<Fragment>{showMyComponent ? <MyComponent /> : <OtherComponent />}</Fragment>

Short-Circuit Evaluation

<Fragment>
  {showPopup && <Popup />}
  ...
</Fragment>

Property Validation

PropTypes

import PropTypes from 'prop-types';

Typechecking with PropTypes

Basic Types

MyComponent.propTypes = {
  email: PropTypes.string,
  seats: PropTypes.number,
  callback: PropTypes.func,
  isClosed: PropTypes.bool,
  any: PropTypes.any,
};

Required Types

MyCo.propTypes = {
  name: PropTypes.string.isRequired,
};

Elements

MyCo.propTypes = {
  // React element
  element: PropTypes.element,

  // num, string, element, or an array of those
  node: PropTypes.node,
};

Enumerables (oneOf)

MyCo.propTypes = {
  direction: PropTypes.oneOf(['left', 'right']),
};

Arrays and Objects

MyCo.propTypes = {
  list: PropTypes.array,
  ages: PropTypes.arrayOf(PropTypes.number),
  user: PropTypes.object,
  user: PropTypes.objectOf(PropTypes.number),
  message: PropTypes.instanceOf(Message),
};
MyCo.propTypes = {
  user: PropTypes.shape({
    name: PropTypes.string,
    age: PropTypes.number,
  }),
};

Use .array[Of].object[Of].instanceOf.shape.

Custom Validation

MyCo.propTypes = {
  customProp: (props, key, componentName) => {
    if (!/matchme/.test(props[key])) {
      return new Error('Validation failed!');
    }
  },
};

Wrapping Up

Your search for Reactjs Cheatsheet appears to have ended. Coding with React and remembering all of its code snippets is a long period of work. It will take time, but sticking to its guidelines, cheatsheets, and roadmaps will help you stay ahead of the game in the long run.

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