为什么我得到“http://localhost:3000/”？ 在反应中使用useNavigate时的路线？

Question

I am using useNavigate to navigate from one page of my website to another when a button is clicked. When I run the site using npm start, when I click the button, the page reloads the current page and the url changes from 'http://localhost:3000' to 'http://localhost:3000/?'

The code is below:

const submitForm = async (e) => {
const res = await fetch("http://localhost:8000/properties")
const jsonData = await res.json()
setProperties(jsonData)
navigate("/list", { state: properties })
}

button element:

<button onClick={() => submitForm()}>Find Properties</button>

For configuring my routes in App.js, I simply have:

export default function App() {
  return (
    <BrowserRouter>
      <div className="App">
        <Routes>
          <Route exact path="/" element={<FormComponent />} />
          <Route path="/list" element={<ListComponent />} />
        </Routes>
      </div>
    </BrowserRouter>
  )
}

Answer 1

Issues

1. It seems this button is very likely rendered within a form element, and when the form is submitted the default form action is not being prevented and the page is reloading.

2. Additionally, it appears the submitForm handler is enqueueing a React state update and then attempting to navigate with the expected updated state.

    const submitForm = async (e) => { const res = await fetch("http://localhost:8000/properties"); const jsonData = await res.json(); setProperties(jsonData); // <-- enqueued state update navigate("/list", { state: properties }); // <-- stale state }

   In React, enqueued state updates are processed asynchronously. You can't enqueue a state update and expect to read the updated state value in the same function/callback scope the update was enqueued in.

3. button elements have type="submit" by default if a type attribute isn't provided.

Solution

1. Move the submitForm callback handler to the form element's onSubmit handler prop.
2. Call preventDefault on the onSubmit event object.
3. Explicitly declare a button type.
4. Pass the fetched JSON data directly in the navigate function, no need to update local state considering the component is likely unmounted soon.

Example:

const submitForm = async (e) => {
  e.preventDefault(); // <-- prevent default form action

  const res = await fetch("http://localhost:8000/properties");
  const jsonData = await res.json();

  navigate("/list", { state: jsonData }); // <-- pass current data
}

...

<form onSubmit={submitForm}>
  ...

  <button type="submit">Find Properties</button>
  ...
</form>