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