instrumental/app/javascript/mastodon/components/dropdown_menu.js

import React from 'react';
import Dropdown, { DropdownTrigger, DropdownContent } from 'react-simple-dropdown';
import PropTypes from 'prop-types';

class DropdownMenu extends React.PureComponent {

  constructor (props, context) {
    super(props, context);
    this.state = {
      direction: 'left'
    };
    this.setRef = this.setRef.bind(this);
    this.renderItem = this.renderItem.bind(this);
  }

  setRef (c) {
    this.dropdown = c;
  }

  handleClick (i, e) {
    const { action } = this.props.items[i];

    if (typeof action === 'function') {
      e.preventDefault();
      action();
      this.dropdown.hide();
    }
  }

  renderItem (item, i) {
    if (item === null) {
      return <li key={ 'sep' + i } className='dropdown__sep' />;
    }

    const { text, action, href = '#' } = item;

    return (
      <li className='dropdown__content-list-item' key={ text + i }>
        <a href={href} target='_blank' rel='noopener' onClick={this.handleClick.bind(this, i)} className='dropdown__content-list-link'>
          {text}
        </a>
      </li>
    );
  }

  render () {
    const { icon, items, size, direction, ariaLabel } = this.props;
    const directionClass = (direction === "left") ? "dropdown__left" : "dropdown__right";

    return (
      <Dropdown ref={this.setRef}>
        <DropdownTrigger className='icon-button' style={{ fontSize: `${size}px`, width: `${size}px`, lineHeight: `${size}px` }} aria-label={ariaLabel}>
          <i className={ `fa fa-fw fa-${icon} dropdown__icon` }  aria-hidden={true} />
        </DropdownTrigger>

        <DropdownContent className={directionClass}>
          <ul className='dropdown__content-list'>
            {items.map(this.renderItem)}
          </ul>
        </DropdownContent>
      </Dropdown>
    );
  }

}

DropdownMenu.propTypes = {
  icon: PropTypes.string.isRequired,
  items: PropTypes.array.isRequired,
  size: PropTypes.number.isRequired,
  direction: PropTypes.string,
  ariaLabel: PropTypes.string
};

DropdownMenu.defaultProps = {
  ariaLabel: "Menu"
};

export default DropdownMenu;