useActionState is a hook that allows you to update state based on the result of a form action.

It's currently only available in React’s Canary and experimental channels. In addition, you need to use a framework that supports React Server Components to get the full benefit of useActionState.

It simplifies managing form state updates based on server-side actions. It's particularly useful with React Server Components (RSC) for faster response times.

📝 Basic example

The most simple example to understand the concept would be that of a form that increments a counter.

import { useActionState } from "react";

async function increment(previousState, formData) {
  return previousState + 1;
}

function StatefulForm({}) {
  const [state, actionToTake] = useActionState(increment, 0);
  return (
    <form>
      {state}
      <button formAction={actionToTake}>Increment</button>
    </form>
  )
}

As you can see the form takes two arguments

• An action function that handles form submission and interacts with the server.
• An initialState object representing the initial form state.
  • The action function itself will receive two arguments - previousState and the formData. In the first call the previousState will be the initialState that would have been initialized when useActionState was called.

And it returns an array containing

• The current form state object
• a actionToTake (you can rename it to whatever makes most sense - see example below) function that you can use as a button formAction handler (example above) or action handler in form component itself (example below).

💡 When <form> is rendered by a Server Component, and a Server Action is passed to the <form>’s action prop, the form is progressively enhanced. This means that forms can be submitted before the JavaScript bundle is loaded 🔥

📝 Example with server actions

Another interesting property the hook returns is the isPending property which can help handle loading states.

// actions.js
'use server'

export default async function incrementLike(prevState, data) {
  // Simulate delay
  return new Promise((resolve, reject) =>
    setTimeout(() => resolve(prevState + 1), 3000)
  )
}

//like.js
'use client'

import incrementLike from './actions'
import { useActionState } from 'react'

function LikeButton() {
  const [likes, likeCountAction, isPending] = useActionState(incrementLike, 0)

  return (
    <>
      <p>Total Likes: {likes}</p>
      <form action={likeCountAction}>
        <button
          type='submit'
          disabled={isPending}
          className="border box-shadow bg-[#fff] p-4 disabled:opacity-50 disabled:cursor-not-allowed"
        >
          Like
        </button>
      </form>
    </>
  )
}

📝 Key Takeaways

• useActionState simplifies managing form state based on server-side actions.
• It's particularly useful with React Server Components (RSC) for faster response times.
• It offers functionalities like isPending to handle loading states during server interactions.

📝 Things to Keep in Mind

• useActionState is currently experimental and might change in future releases.
• You need a framework that supports React Server Components to utilize the full potential of this hook.

Happy coding!