using setstate in child component code example

Example 1: pass setstate to child

//ChildExt component
class ChildExt extends React.Component {
    render() {
        return (<div><button onClick={() => this.props.handleForUpdate('someNewVar')}>Push me</button></div>
        )}
}
//Parent component
class ParentExt extends React.Component {
  constructor(props){
    super(props);
    this.state = {lol: false }
  }

    handleForUpdate(someArg){
            this.setState({lol: true});
      		console.log(someArg);
    }
  //Notice how we don't pass the arguments into the bind.this even though it does take an argument.
    render() {
        return (<ChildExt handleForUpdate={this.handleForUpdate.bind(this)} />)
    }
}

Example 2: react setState

incrementCount() {
  // Note: this will *not* work as intended.
  this.setState({count: this.state.count + 1});
}

handleSomething() {
  // Let's say `this.state.count` starts at 0.
  this.incrementCount();
  this.incrementCount();
  this.incrementCount();
  // When React re-renders the component, `this.state.count` will be 1, but you expected 3.

  // This is because `incrementCount()` function above reads from `this.state.count`,
  // but React doesn't update `this.state.count` until the component is re-rendered.
  // So `incrementCount()` ends up reading `this.state.count` as 0 every time, and sets it to 1.

  // The fix is described below!
}