React Dropdown Component

class Dropdown extends React.Component {

  constructor(props) {
    super(props);

    this.toggleDropdown = this.toggleDropdown.bind(this);
    this.handleMouseEvent = this.handleMouseEvent.bind(this);
    this.handleBlurEvent = this.handleBlurEvent.bind(this);
    this.hasFocus = this.hasFocus.bind(this);

    this.state = {
      show: false
    };
  }

  componentDidMount() {
    document.addEventListener('mouseup', this.handleMouseEvent);
    this.dropdown.addEventListener('focusout', this.handleBlurEvent);
  }

  hasFocus(target) {
    if (!this.dropdown) {
      return false;
    }
    var dropdownHasFocus = false;
    var nodeIterator = document.createNodeIterator(this.dropdown, NodeFilter.SHOW_ELEMENT, null, false);
    var node;    

    while(node = nodeIterator.nextNode()) {
      if (node === target) {
        dropdownHasFocus = true;
        break;
      }
    }

    return dropdownHasFocus;
  }

  handleBlurEvent(e) {
    var dropdownHasFocus = this.hasFocus(e.relatedTarget);

    if (!dropdownHasFocus) {
      this.setState({
        show: false
      });
    }    
  }

  handleMouseEvent(e) {
    var dropdownHasFocus = this.hasFocus(e.target);

    if (!dropdownHasFocus) {
      this.setState({
        show: false
      });
    }
  }

  toggleDropdown() {
    this.setState({
      show: !this.state.show
    });
  }

  render() {
    return (
      <div className={`dropdown ${this.state.show ? 'show' : ''}`} ref={(dropdown) => this.dropdown = dropdown}>
        <button 
          className="btn btn-secondary dropdown-toggle" 
          type="button" 
          id="dropdownMenuButton" 
          data-toggle="dropdown" 
          aria-haspopup="true" 
          aria-expanded={this.state.show}
          onClick={this.toggleDropdown}>
          Dropdown button
        </button>
        <div 
          className="dropdown-menu" 
          aria-labelledby="dropdownMenuButton">
          <a className="dropdown-item" href="#nogo">Item 1</a>
          <a className="dropdown-item" href="#nogo">Item 2</a>
        </div>
      </div>
    );
  }
}