Created
October 22, 2019 16:13
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A simple example of useEffect
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| import React, {useState, useEffect} from "react" | |
| import randomcolor from "randomcolor" | |
| function App() { | |
| const [count, setCount] = useState(0) | |
| const [color, changeColor] = useState(randomcolor) | |
| useEffect(() => { | |
| const intervalId = setInterval(() => | |
| setCount(prevCount => prevCount + 1), 1000 | |
| ) | |
| return () => clearInterval(intervalId) | |
| }, []) | |
| useEffect(() => { | |
| changeColor(randomcolor()) | |
| }, [count]) | |
| return ( | |
| <div> | |
| <h1 style={{color: color}}>{count}</h1> | |
| </div> | |
| ) | |
| } | |
| export default App |
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| <html> | |
| <head> | |
| <link rel="stylesheet" href="style.css"> | |
| </head> | |
| <body> | |
| <div id="root"></div> | |
| <script src="index.pack.js"></script> | |
| </body> | |
| </html> |
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| import React from "react" | |
| import ReactDOM from "react-dom" | |
| import App from "./App" | |
| ReactDOM.render(<App />, document.getElementById("root")) |
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| div { | |
| display: flex; | |
| flex-direction: column; | |
| align-items: center; | |
| justify-content: center; | |
| } | |
| h1 { | |
| font-size: 3em; | |
| } | |
| button { | |
| border: 1px solid lightgray; | |
| background-color: transparent; | |
| padding: 10px; | |
| border-radius: 4px; | |
| } | |
| button:hover { | |
| cursor: pointer; | |
| } | |
| button:focus { | |
| outline:0; | |
| } |
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