[Solved]-How can I change a child's state from the parent component-Reactjs

 reactDOM.unmount(document.body);
 reactDOM.render(<App />, document.body);

class App extends React.Component {
  state = {
    name: "",
    select: "",
  }

  defaultState = {
    name: "",
    select: "",
  };

  formRef = React.createRef();

  handleChane = e => this.setState( {
    [ e.target.name ]: e.target.value,
  } );

  handleSubmit = ( e ) => {
    e.preventDefault();
    alert( JSON.stringify( this.state ) );
    this.setState( this.defaultState );
    this.formRef.current.reset();
  }

  render() {
    console.log( this.state );
    return (
      <form ref={this.formRef} onSubmit={this.handleSubmit} >
        <Input onChange={this.handleChane} />
        <Select onChange={this.handleChane} />
        <button>Send</button>
      </form>
    );
  }
}

const Input = props => (
  <div>
    <input onChange={props.onChange} name="name" />
  </div>
);

const Select = props => (
  <div>
    <select onChange={props.onChange} name="select">
      <option>Choose one</option>
      <option>Foo</option>
      <option>Bar</option>
      <option>Baz</option>
    </select>
  </div>
);