Understand and use useState Hooks in React

In this article we are going to talk about useState hooks in React and how to use it.

useState Hooks ? What is it ? 😳

useState is a React hooks that allow us to use and to modify the state in our function component(before called stateless component) without to write a class component and setState method.
In the previous version of React before the react@16.8, the using of state and update the state in our component was like this :

import React from 'react'

class App extends React.Component() {
  constructor(props) {
    super(props)
    this.state = {
      name:"Emmanuel",
    }
    this.handleChange = this.handleChange.bind(this)
  }

  handleChange(e){
    this.setState({name:e.target.value})
  }

  render(){
      return(
           <div>
            <p>{this.state.name}</p>
            <input value={this.state.name} type="text" name="name" handleChange={this.handleChange}/>
        </div>
      )
  }
}

Since the hooks are been introduced in React, the way to use the state and to modify the state are become easy. We are going to modify the previous code and to write a functional component with useState hooks.

import React, { useState } from 'react';

function App(props){
  const [name, setName] = useState('Emmanuel')

  function handleChange(e){
    setName(e.target.value)
  }

  return(
    <div>
      <p>{name}</p>
        <input value={name} type="text" name="name" onChange={handleChange}/>
    </div>
    )
}

Like we see in the fist line of our code, we have imported the useState hooks. the setName function passed to onClick event allow to update our name state.

How useState hooks works

const [state, setState] = useState(initialState);

It returns a stateful value, and a function to update it.During the initial render, the returned state is the same as the value passed as the first argument (initialState). The setState function is used to update the state. It accepts a new state value and enqueues a re-render of the component. During subsequent re-renders, the first value returned by useState will always be the most recent state after applying updates. React guarantees that setState function identity is stable and won’t change on re-renders.

The state value can be a object, array, number, string, boolean, etc...

Note ❗

If you want to use the useState hooks in your code and if you have already write your code with the Class method, please don't delete your code, you can update the version of your React application (react and react-dom) to the new version supported the hooks and continue to build your application using the useState in the new component created.