pass a function to child component react code example

Example 1: pass state to child react

class SomeParentComponent extends React.Component {
  constructor(props) {
    super(props);
    this.state = {color: 'red'};
  }
  render() {
    return <SomeChildComponent color={this.state.color} />;
  }
}

Example 2: pass element from child to parent react

Parent:

<div className="col-sm-9">
     <SelectLanguage onSelectLanguage={this.handleLanguage} /> 
</div>

Child:

handleLangChange = () => {
    var lang = this.dropdown.value;
    this.props.onSelectLanguage(lang);            
}

Example 3: pass function with parameter as prop

class SomeComponent extends Component{

    constructor(props){
        super(props);
        //does whatever stuff        
        this.myFunction = this.myFunction.bind(this);

    }

    //(only applicable to raw and normal forms)
    myFunction(param){
        console.log('do something: ', param);
    }

    render(){
     return (<div><ChildComponent1 myFunction={this.myFunction}/></div>)
    }
}

class ChildComponent1{
      render(){
  return (<div><ChildComponent2 myFunction={this.props.myFunction}/></div>)
    }
}

class ChildComponent2{
      render(){
  return (<Button onClick={()=>this.props.myFunction(param)}>SomeButton</Button>)
    }
}