How to apply useEffect based on form submission in React?

Question

I am trying to make an API call inside a functional component, based on a form submission:

const SearchForm = () => {
    const [keywords, setKeywords] = useState('')
    const [fetchedData, setFetchedData] = useState('')

    const handleSubmit = (e) => {
        e.preventDefault();
        useEffect(() => {
            async function fetchData() {
                const {data} = await axios.post('http://127.0.0.1:8000/api/posts/', keywords)
                setFetchedData(data);
            }
            fetchData()
        })
    }

    return (
        <div>
            <form onSubmit={ handleSubmit }>
                <div className='input-field'>
                <input placeholder="Search whatever you wish" 
                    type="text"
                    value={keywords}
                    onChange={(e) => setKeywords(e.target.value)}
                />
                </div>
            </form>
        </div>
    )
}

However when I try this, the following error shows up:

React Hook "useEffect" is called in function "handleSubmit" which is neither a React function component or a custom React Hook function  react-hooks/rules-of-hooks

How do I carry this out?

Answer 1

Because it is not how useEffect used for. You don't need to call it inside handler either.

From the documentation :

Only Call Hooks from React Functions Don’t call Hooks from regular JavaScript functions. Instead, you can:

✅ Call Hooks from React function components.

✅ Call Hooks from custom Hooks (we’ll learn about them on the next page). By following this rule, you ensure that all stateful logic in a component is clearly visible from its source code.

If you want fetch data onload of your functional component, you may use useEffect like this :

  useEffect(() => {
    fetchData()
  }, [])

And you want your fetch call to be triggered with button click :

const handleSubmit = e => {
    e.preventDefault()
    fetchData()
  }

So whole code will look like :

const SearchForm = () => {
  const [keywords, setKeywords] = useState('')
  const [fetchedData, setFetchedData] = useState('')

  async function fetchData() {
    const { data } = await axios.post(
      'http://127.0.0.1:8000/api/posts/',
      keywords
    )
    setFetchedData(data)
  }

  useEffect(() => {
    fetchData()
  }, [])

  const handleSubmit = e => {
    e.preventDefault()
    fetchData()
  }

  return (
    <div>
      <form onSubmit={handleSubmit}>
        <div className="input-field">
          <input
            placeholder="Search whatever you wish"
            type="text"
            value={keywords}
            onChange={e => setKeywords(e.target.value)}
          />
        </div>
      </form>
    </div>
  )
}