React: Pass data from Child to Parent Component

ChildtoParentDataPass.js

import React, { Component } from "react";
import { render } from "react-dom";

const styles = {
  fontFamily: "sans-serif",
  textAlign: "center"
};

class ChildComponent extends Component {
  state = {
    selectedCode: "",
    selectedLanguage: []
  };

  handleLangChange = () => {
    let lang = "French";
    this.props.onSelectLanguage(lang);
  };

  render() {
    return (
      <div>
        <button onClick={this.handleLangChange}>click</button>
      </div>
    );
  }
}

// App = parent
class App extends Component {
  constructor(props) {
    super(props);
    this.state = {
      language: ""
    };
  }

  handleLanguage = (langValue) => {
    this.setState({ language: langValue });
  };

  render() {
    return (
      <div style={styles}>
        <div>
          <ChildComponent onSelectLanguage={this.handleLanguage} />
        </div>
        <h2>{this.state.language}</h2>
      </div>
    );
  }
}

/*
Will output: [Click] French
*/

render(<App />, document.getElementById("root"));