Hello Developers 👋

I would like to share something I recently got to know, so the background is, in my project I was using useState value right after updating it and I was getting previous value(not updated value) and to my surprise I found out that useState hook is asynchronous

what it is?

Basically, the thing is you don't get update value right after updating state.

What is the work around/solution?

We can use the useEffect hook and add our state in the dependence array, and we will always get the updated value.

Show me the code 🤩🤩🤩

import { useState } from "react";

export default function CountWithoutEffect() {
    const [count, setCount] = useState(0);
    const [doubleCount, setDoubleCount] = useState(count * 2);
    const handleCount = () => {
        setCount(count + 1);
        setDoubleCount(count * 2); // This will not use the latest value of count
    };
    return (
        <div className="App">
            <div>
                <h2>Count Without useEffect</h2>
                <h3>Count: {count}</h3>
                <h3>Count * 2: {doubleCount}</h3>
                <button onClick={handleCount}>Count++</button>
            </div>
        </div>
    );
}

Here we have very simple and stright forward component.
On button click we are updating two states and one state is dependent on other state.
The doubleCount will be one step behind count.
Check out the Live Demo

Solving this issue 🧐🧐🧐

This can be easily solve with useEffect hook, let's see the code


import { useState, useEffect } from "react";

export default function CountWithEffect() {
    const [count, setCount] = useState(0);
    const [doubleCount, setDoubleCount] = useState(count * 2);
    const handleCount = () => {
        setCount(count + 1);
    };

    useEffect(() => {
        setDoubleCount(count * 2); // This will always use latest value of count
    }, [count]);

    return (
        <div>
            <h2>Count with useEffect</h2>
            <h3>Count: {count}</h3>
            <h3>Count * 2: {doubleCount}</h3>
            <button onClick={handleCount}>Count++</button>
        </div>
    );
}

Here, when ever count changes we are updating doubleCount
Check out the live Demo

Closing here 👋👋👋

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React useState hook is asynchronous!

Mohammed Nadeem Shareef