Last active
March 29, 2020 20:09
-
-
Save imsarvesh/a7a3b2c207845f14c3f47dc92657734f to your computer and use it in GitHub Desktop.
useMemo Example
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
import { useState, useMemo } from 'react'; | |
// Usage | |
function App() { | |
const [count, setCount] = useState(0); | |
const [wordIndex, setWordIndex] = useState(0); | |
const words = ['hey', 'this', 'is', 'cool']; | |
const word = words[wordIndex]; | |
const computeLetterCount = word => { | |
let i = 0; | |
while (i < 1000000000) i++; | |
return word.length; | |
}; | |
const letterCount = useMemo(() => computeLetterCount(word), [word]); | |
return ( | |
<div style={{ padding: '15px' }}> | |
<h2>Compute number of letters (slow 🐌)</h2> | |
<p>"{word}" has {letterCount} letters</p> | |
<button | |
onClick={() => { | |
const next = wordIndex + 1 === words.length ? 0 : wordIndex + 1; | |
setWordIndex(next); | |
}} | |
> | |
Next word | |
</button> | |
<h2>Increment a counter (fast ⚡️)</h2> | |
<p>Counter: {count}</p> | |
<button onClick={() => setCount(count + 1)}>Increment</button> | |
</div> | |
); | |
} | |
ReactDOM.render(<App/>, mountNode); |
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment