update state react code example

Example 1: state with react functions

import React, { useState } from 'react';

function Example() {
  // Declare a new state variable, which we'll call "count"
  const [count, setCount] = useState(0);

  return (
    <div>
      <p>You clicked {count} times</p>
      <button onClick={() => setCount(count + 1)}>
        Click me
      </button>
    </div>
  );
}

Example 2: how to update array in react state

this.setState(prevState => ({
  arrayvar: [...prevState.arrayvar, newelement]
}))

Example 3: set state

class App extends React.Component {

state = { count: 0 }

handleIncrement = () => {
  this.setState({ count: this.state.count + 1 })
}

handleDecrement = () => {
  this.setState({ count: this.state.count - 1 })
}
  render() {
    return (
      <div>
        <div>
          {this.state.count}
        </div>
        <button onClick={this.handleIncrement}>Increment by 1</button>
        <button onClick={this.handleDecrement}>Decrement by 1</button>
      </div>
    )
  }
}

Example 4: state with react functions

class Example extends React.Component {
  constructor(props) {
    super(props);
    this.state = {
      count: 0
    };
  }

  render() {
    return (
      <div>
        <p>You clicked {this.state.count} times</p>
        <button onClick={() => this.setState({ count: this.state.count + 1 })}>
          Click me
        </button>
      </div>
    );
  }
}

Example 5: setstate react js

constructor(props) {
        super(props);
        this.state = {
            isActive: true,
        };
    }

    checkStatus = () => {
        this.setState({		// use this function
            'isActive' : !this.state.isActive,
        });
    }

Example 6: update state in react

You have to use setState() for updating state in React
{
  hasBeenClicked: false,
  currentTheme: 'blue',
}

setState({
	hasBeenClicked: true
});