React Dropdown Component

Dropdowns are toggleable, contextual overlays for displaying lists of links and more. They are made interactive with the included Bootstrap dropdown. Dropdown are toggled by clicking.

Create 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>
    );
  }
}

Now we have react <Dropdown /> component and we can use this in our functional or class components easily.

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