react check state change 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: 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 3: 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 (
      

        
{this.state.count}
        Click Me
      
    )
  }
}

export default ButtonCounter

Example 4: set state

setState({ searchTerm: event.target.value })

Example 5: react change state

// React change state
this.setState({state to change:value});