React Sidebar

Sidebar.js

import React from "react";
import ReactDOM from "react-dom";
import "./styles.css";
import classNames from "classnames";

class Sidebar extends React.Component {
  constructor(props) {
    super(props);
    this.state = {
      showMenu: false
    };
  }
  componentDidMount = () => {
    document.addEventListener("click", this.handleClickOutside, true);
  };

  componentWillUnmount = () => {
    document.removeEventListener("click", this.handleClickOutside, true);
  };
  toggleMenu = () => {
    this.setState({ showMenu: !this.state.showMenu });
  };
  handleClickOutside = event => {
    const domNode = ReactDOM.findDOMNode(this);

    if (!domNode || !domNode.contains(event.target)) {
      this.setState({
        showMenu: false
      });
    }
  };

  render() {
    const showMenu = this.state.showMenu;
    const sidebarClass = classNames({
      sidebar: true,
      "sidebar-menu-expanded": showMenu,
      "sidebar-menu-collapsed": !showMenu
    });

    const elementsClass = classNames({
      "expanded-element": true,
      "is-hidden": !showMenu
    });

    return (
      <nav className={sidebarClass}>
        <img
          className="menuIcon"
          src={"https://png.icons8.com/menu/ffffff"}
          onClick={this.toggleMenu}
        />
        <ul>
          <li>
            <a className="expandable" href="#" title="Setting">
              <img src={"https://png.icons8.com/setting/ffffff"} alt="" />
              <span className={elementsClass}>Setting</span>
            </a>
          </li>
        </ul>
      </nav>
    );
  }
}

export default Sidebar;

styles.css

.menuIcon {
  margin-top: 70px;
  cursor: pointer;
}
nav.sidebar-menu-collapsed {
  width: 70px;
}
nav.sidebar-menu-expanded {
  width: 211px;
  z-index: 1;
}
nav.sidebar {
  position: fixed;
  top: 0px;
  left: 0px;
  height: 100%;
  background: none repeat scroll 0 0 #000;
  color: white;
  padding: 20px 10px;
}
nav.sidebar a#justify-icon {
  outline: 0;
  color: white;
  font-size: 24px;
  font-style: normal;
}
nav.sidebar ul {
  margin: 0;
  padding: 0;
}
nav.sidebar ul li {
  margin: 0;
  padding: 0;
  margin-top: 20px;
  list-style-type: none;
}
nav.sidebar ul li a.expandable {
  outline: 0;
  color: white;
  text-decoration: none;
  font-size: 20px;
}
nav.sidebar ul li a.expandable:hover {
  color: #bbb;
}
nav.sidebar ul li a.expandable span.expanded-element {
  color: #fff;
  margin-left: 12px;
  font-size: 16px;
  position: relative;
  bottom: 2px;
}
nav.sidebar ul li.active {
  background: none repeat scroll 0 0 black;
  border-radius: 4px;
  text-align: center;
  margin-left: -4px;
  padding: 4px;
}
nav.sidebar ul li.active a.expandable {
  color: white !important;
}
nav.sidebar ul li.active a.expandable:hover {
  color: white !important;
}