How can I get the state value immediately after changing the state?

Question

I am trying to get the state name value immediately after setting it? How can we get the value instantly, or there is any method to do this that I can get the value in the alert?

import { useState } from 'react';
    
export default function FeedbackForm() {
  const [name, setName] = useState('');

  async function handleClick() {
    setName(prompt('What is your name?'));
    await alert(`Hello, ${name}!`);
  }

  return (
    <button onClick={handleClick}>
      Greet
    </button>
  );
}

Answer 1

One simple way that I would suggest you here is to use constant

for example ->

import { useState } from 'react';

export default function FeedbackForm() {
  const [name, setName] = useState('');

 async function handleClick() {
    const newName = prompt('What is your name?');
    setName(newName);
    await alert(`Hello, ${newName}!`);
  }

  return (
    <button onClick={handleClick}>
      Greet
    </button>
  );
}

This way you will be able to use updated state value. I hope it solves the use case for your code

Answer 2

You cannot get the value immediately, as the function was created when the value of name was ''. Once the event handler has finished executing, React will re-render the component, which will now have the updated value for name.

You can store the returned value from the prompt in a local variable, and then use that instead:

function handleClick() {
  const enteredName = prompt('What is your name?');
  setName(enteredName)
  alert(`Hello, ${enteredName}!`);
}

Also note that I have not set the handleClick function as async. alert does not return a Promise, so using await in front of it has no effect.

Answer 3

You use useEffect to do something whenever state changes.

export default function FeedbackForm() {
  const [name, setName] = useState('');

  useEffect(() => {
    alert(name);
  },[name]) // <- this is the dependency, useEffect is called whenever name changes.

 async function handleClick() {
    setName(prompt('What is your name?'));
//    await alert(`Hello, ${name}!`);
  }

  return (
    <button onClick={handleClick}>
      Greet
    </button>
  );
}```

Answer 4

React uses renders to track changes made to state. Once the event handler finishes running, React triggers a re-render and that render will have the new state value. You can then simply read the (now updated) state during this render.

Nothing is stopping you from using the value returned from your prompt right away, but you would simply be reading a plain old JS variable during the execution of the handler (while React state on the other hand persists between renders).

If you don't need to get the name state every time the component renders but only it when name changes, you can use the useEffect hook.

Example

export default function FeedbackForm() {
  const [name, setName] = useState(null);

  console.log(`component rendered, current name is ${name}`);

  useEffect(() => {
    console.log("effect running...");
    if (name === null) {
      return;
    }
    console.log(`name has changed to ${name}`);
    alert(`Hello, ${name}!`);
  }, [name]);

  function handleClick() {
    const newName = prompt("what is your name?");
    setName(newName);
  }

  return (
    <div>
      <button onClick={handleClick}>Greet</button>
      <p>Name: {name}</p>
    </div>
  );
}

https://codesandbox.io/s/react-name-prompt-6qknz6