setstate react class component 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: 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 3: setstate react js

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

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

Example 4: lifecycle method react

INITIALIZATION= setup props and state 
MOUNTING= constructor->componentWillMount->render->componentDidMount//Birth
UPDATE= shouldComponentUpdate->componentWillUpdate->render
  		->componentDidUpdate //Growth
UNMOUNTING= componentWillUnmount //Death

Example 5: setstate in react

Functional Component
const [counter, setCounter] = useState(0);

setCouter(counter + 1);

Example 6: change state in react

import React, {Component} from 'react';

class ButtonCounter extends Component {
  constructor() {
    super()
    // initial state has count set at 0
    this.state = {
      count: 0
    }
  }

  handleClick = () => {
    // when handleClick is called, newCount is set to whatever this.state.count is plus 1 PRIOR to calling this.setState
    let newCount = this.state.count + 1
    this.setState({
      count: newCount
    })
  }

  render() {
    return (
      <div>
        <h1>{this.state.count}</h1>
        <button onClick={this.handleClick}>Click Me</button>
      </div>
    )
  }
}

export default ButtonCounter