[React] Reference a node using createRef() in React 16.3

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

class App extends React.Component {
  fullName = React.createRef();

  handleBlur = () => {
    this.fullName.current.blur();
  };

  handleFocus = () => {
    this.fullName.current.focus();
  };

  render() {
    return (
      <div className="section">
        <div className="field">
          <label className="label">Full Name</label>
          <div className="control">
            <input className="input" ref={this.fullName} type="text" />
          </div>
        </div>
        <button
          className="button is-link is-outlined"
          onClick={this.handleFocus}
        >
          Focus
        </button>{" "}
        <button
          className="button is-danger is-outlined"
          onClick={this.handleBlur}
        >
          Blur
        </button>
      </div>
    );
  }
}

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