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React (work in progress) Cheat sheet

ericchapman profile image Eric Chapman ・3 min read

I don't use React often and so whenever I need to do even the smallest thing in React, I have to check out the documentation, a tutorial, or post a question on a forum.

That's why I decided to do this memory aid and given that my memory is not that good I thought why not make a monstrous memory aid with all the concepts I know about React.

So I can read it from time to time and thereby strengthen my knowledge of React.

It will take couples of days to put all that together so every day I will post an updated Cheat Sheet version until the final version.

If you have ideas or recommendation do not hesitate and do so in the comments section.

Let's start right now with the first version...

React Cheat Sheet (draft day 1)

 

Create a React App

// Create a new app
npx create-react-app my-app-name

// Run the created app
cd my-app-name
yarn start

// http://localhost:3000
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First React functional Component

  • No need to import React from 'react' (since React 17)
  • Must have uppercase first letter
  • Must return JSX

(src/App.js)

// React component
function App(){
  return <h1>Hello World</h1>
} 

export default App;
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How this component get render to the browser? The main project file is src/index.js and in that file there are instruction to render the component

ReactDOM.render(<App />, document.getElementById('root'))
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The App component will then be rendered inside public/index.html 'root' div

JSX Rules

Return a single element (only one parent element)

// not valid
return <h1>Hello world</h1><h2>Hi!</h2>

// valid with fragment. 
return (
    <>
        <h1>Hello World</h1>
        <h2>Hi!</h2>
    </>
)
// Noted the parenthesis for multi-line formatting
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Use className instead of class
Also all attribute name need to be camelCase

// not valid
return (
    <div class="title">
        Hello World
    </div>
)

// valid
return (
    <div className="title">
    </div>
)

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Close every element

return (
    <img src="http:example.com/image.jpg" />
    <input type="text" name="first_name" />
)
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Nested Components

// Arrow function shorthand component
const Person = () => <h1>Mike Taylor</h1>

// Arrow function component
const Message = () => {
    return <h1>Hello</h1>
}

// Function component
function HelloWorld(){
  return (
      <>
          <Message />
          <Person />
      </>
  )
} 
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Component CSS

(src/App.css)

h1 {
    color: red;
}

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(src/App.js)
Import the CSS file

import './App.css'

function App(){
  return <h1>Hello World</h1>
} 
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Inline CSS

function App(){
  return <h1 style={{ color: 'red' }}>Hello World</h1>
} 
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Javascript in JSX

  • Enclose between {}
  • Must be an expression (return a value)
function App(){
    const name = 'Mike'
    return (
      <>
          <h1>Hello {name}</h1>
          <p>{name === 'Mike' ? '(admin)': '(user)'}</p>
      </>
    )
} 
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Component Properties (Props)

function App()
    return <Person name='Mike' age={29} />
} 

const Person = (props) => {
    return <h1>Name: {props.name}, Age: {props.age}</h1>
}

// or props object deconstructing
const Person = ({name, age}) => {
    return <h1>Name: {name} Age: {age}</h1>
}
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Children Props (slot)

function App()
    return (
        <Person name='Mike' age={29}>
            Hi, this is a welcome message
        </Person>
    )
} 

const Person = (props) => {
    return (
        <h1>Name: {props.name}, Age: {props.age}</h1>
        <p>{props.children}</p>
    )
}

// or props object deconstructing
const Person = ({name, age, children}) => {
    return (
        <h1>Name: {name} Age: {age}</h1>
        <p>{children}</p>
    )
}
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Conclusion

That's it for today. We still have a lot to do, so see you tomorrow... If you want to be sure to miss nothing click follow me!

I am new on twitter so if you want to make me happy
Follow me!: Follow @justericchapman

Discussion (3)

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michaelcurrin profile image
Michael • Edited

Hi. I am not so familiar with React. so this looks useful for me.

I have a React cheatsheet here. I liked some of your points so worked them into my JSX page. Also I hadn't see destructuring props without props variable so added it to my Props page.
michaelcurrin.github.io/dev-cheats...

I also like to use the result of running the quickstart command as repo and live site, for reference.

github.com/MichaelCurrin/react-qui...

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cyrdodi_77 profile image
Dodi Yulian

Thank you, it's way better than my cheat sheet, probably I'll use yours

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nashmeyah profile image
Nashmeyah

This is so dang helpful!