46 lines
918 B
Markdown
46 lines
918 B
Markdown
---
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title: React usePrevious hook
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type: snippet
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language: react
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tags: [hooks,state,effect]
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author: chalarangelo
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cover: couch-laptop
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dateModified: 2020-11-16T14:17:53+02:00
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---
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Stores the previous state or props.
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- Create a custom hook that takes a `value`.
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- Use the `useRef()` hook to create a `ref` for the `value`.
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- Use the `useEffect()` hook to remember the latest `value`.
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```jsx
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const usePrevious = value => {
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const ref = React.useRef();
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React.useEffect(() => {
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ref.current = value;
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});
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return ref.current;
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};
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```
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```jsx
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const Counter = () => {
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const [value, setValue] = React.useState(0);
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const lastValue = usePrevious(value);
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return (
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<div>
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<p>
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Current: {value} - Previous: {lastValue}
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</p>
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<button onClick={() => setValue(value + 1)}>Increment</button>
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</div>
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);
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};
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ReactDOM.createRoot(document.getElementById('root')).render(
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<Counter />
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);
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```
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