component 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 (
    

      
You clicked {count} times
       setCount(count + 1)}>
        Click me
      
    
  );
}

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 (
      

        

          {this.state.count}
        
        Increment by 1
        Decrement by 1
      
    )
  }
}

Example 3: state with react functions

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

  render() {
    return (
      

        
You clicked {this.state.count} times
         this.setState({ count: this.state.count + 1 })}>
          Click me
        
      
    );
  }
}

Example 4: lifecycle methods react

Every component in React goes through a lifecycle of events. I like to think of them as going through a cycle of birth, growth, and death.

Mounting – Birth of your component
Update – Growth of your component
Unmount – Death of your component

Example 5: state in react

class BalanceInquiry extends Component {
  constructor(props) {
    super(props);
    this.state = {
      totalIncome: 0,
    };
  }

  render() {
    return 
totalIncome {this.state.totalIncome}
;
  }
}

Example 6: reading state react

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