66 lines
2.0 KiB
Markdown
66 lines
2.0 KiB
Markdown
---
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title: Textarea with word limit
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tags: components,input,state,callback,effect,event
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expertise: intermediate
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cover: blog_images/painters-desk.jpg
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firstSeen: 2019-02-20T18:22:22+02:00
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lastUpdated: 2021-10-13T19:29:39+02:00
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---
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Renders a textarea component with a word limit.
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- Use the `useState()` hook to create a state variable, containing `content` and `wordCount`. Use the `value` prop and `0` as the initial values respectively.
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- Use the `useCallback()` hooks to create a memoized function, `setFormattedContent`, that uses `String.prototype.split()` to turn the input into an array of words.
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- Check if the result of applying `Array.prototype.filter()` combined with `Boolean` has a `length` longer than `limit`. If it does, trim the input. Otherwise return the raw input, updating state accordingly in both cases.
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- Use the `useEffect()` hook to call the `setFormattedContent` method on the value of the `content` state variable during the initial render.
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- Bind the `onChange` event of the `<textarea>` to call `setFormattedContent` with the value of `event.target.value`.
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```jsx
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const LimitedWordTextarea = ({ rows, cols, value, limit }) => {
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const [{ content, wordCount }, setContent] = React.useState({
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content: value,
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wordCount: 0
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});
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const setFormattedContent = React.useCallback(
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text => {
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let words = text.split(' ').filter(Boolean);
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if (words.length > limit) {
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setContent({
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content: words.slice(0, limit).join(' '),
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wordCount: limit
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});
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} else {
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setContent({ content: text, wordCount: words.length });
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}
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},
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[limit, setContent]
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);
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React.useEffect(() => {
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setFormattedContent(content);
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}, []);
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return (
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<>
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<textarea
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rows={rows}
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cols={cols}
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onChange={event => setFormattedContent(event.target.value)}
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value={content}
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/>
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<p>
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{wordCount}/{limit}
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</p>
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</>
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);
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};
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```
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```jsx
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ReactDOM.render(
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<LimitedWordTextarea limit={5} value="Hello there!" />,
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document.getElementById('root')
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);
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```
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