Textarea with word limit

React, Components, Input, State, Callback, Effect, Event · Oct 13, 2021

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.
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>
    </>
  );
};
ReactDOM.render(
  <LimitedWordTextarea limit={5} value="Hello there!" />,
  document.getElementById('root')
);

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