<div class="layout has-sidebar fixed-sidebar fixed-header">
  <aside id="sidebar" class="sidebar break-point-lg has-bg-image">
    <div class="image-wrapper">
      <img src="https://user-images.githubusercontent.com/25878302/144499035-2911184c-76d3-4611-86e7-bc4e8ff84ff5.jpg" alt="sidebar background" />
    </div>
    <div class="sidebar-layout">
      <div class="sidebar-header">
        <span style="
                text-transform: uppercase;
                font-size: 15px;
                letter-spacing: 3px;
                font-weight: bold;
              ">Pro Sidebar</span>
      </div>
      <div class="sidebar-content">
        <nav class="menu open-current-submenu">
          <ul>
            <li class="menu-item sub-menu">
              <a href="#">
                <span class="menu-icon">
                  <i class="ri-vip-diamond-fill"></i>
                </span>
                <span class="menu-title">Components</span>
                <span class="menu-suffix">&#x1F525;</span>
              </a>
              <div class="sub-menu-list">
                <ul>
                  <li class="menu-item">
                    <a href="#">
                      <span class="menu-title">Grid</span>
                    </a>
                  </li>
                  <li class="menu-item">
                    <a href="#">
                      <span class="menu-title">Layout</span>
                    </a>
                  </li>
                  <li class="menu-item sub-menu">
                    <a href="#">
                      <span class="menu-title">Forms</span>
                    </a>
                    <div class="sub-menu-list">
                      <ul>
                        <li class="menu-item">
                          <a href="#">
                            <span class="menu-title">Input</span>
                          </a>
                        </li>
                        <li class="menu-item">
                          <a href="#">
                            <span class="menu-title">Select</span>
                          </a>
                        </li>
                        <li class="menu-item sub-menu">
                          <a href="#">
                            <span class="menu-title">More</span>
                          </a>
                          <div class="sub-menu-list">
                            <ul>
                              <li class="menu-item">
                                <a href="#">
                                  <span class="menu-title">CheckBox</span>
                                </a>
                              </li>
                              <li class="menu-item">
                                <a href="#">
                                  <span class="menu-title">Radio</span>
                                </a>
                              </li>
                              <li class="menu-item sub-menu">
                                <a href="#">
                                  <span class="menu-title">Want more ?</span>
                                  <span class="menu-suffix">&#x1F914;</span>
                                </a>
                                <div class="sub-menu-list">
                                  <ul>
                                    <li class="menu-item">
                                      <a href="#">
                                        <span class="menu-prefix">&#127881;</span>
                                        <span class="menu-title">You made it </span>
                                      </a>
                                    </li>
                                  </ul>
                                </div>
                              </li>
                            </ul>
                          </div>
                        </li>
                      </ul>
                    </div>
                  </li>
                </ul>
              </div>
            </li>
            <li class="menu-item sub-menu">
              <a href="#">
                <span class="menu-icon">
                  <i class="ri-bar-chart-2-fill"></i>
                </span>
                <span class="menu-title">Charts</span>
              </a>
              <div class="sub-menu-list">
                <ul>
                  <li class="menu-item">
                    <a href="#">
                      <span class="menu-title">Pie chart</span>
                    </a>
                  </li>
                  <li class="menu-item">
                    <a href="#">
                      <span class="menu-title">Line chart</span>
                    </a>
                  </li>
                  <li class="menu-item">
                    <a href="#">
                      <span class="menu-title">Bar chart</span>
                    </a>
                  </li>
                </ul>
              </div>
            </li>
            <li class="menu-item sub-menu">
              <a href="#">
                <span class="menu-icon">
                  <i class="ri-shopping-cart-fill"></i>
                </span>
                <span class="menu-title">E-commerce</span>
              </a>
              <div class="sub-menu-list">
                <ul>
                  <li class="menu-item">
                    <a href="#">
                      <span class="menu-title">Products</span>
                    </a>
                  </li>
                  <li class="menu-item">
                    <a href="#">
                      <span class="menu-title">Orders</span>
                    </a>
                  </li>
                  <li class="menu-item">
                    <a href="#">
                      <span class="menu-title">credit card</span>
                    </a>
                  </li>
                </ul>
              </div>
            </li>
            <li class="menu-item sub-menu">
              <a href="#">
                <span class="menu-icon">
                  <i class="ri-global-fill"></i>
                </span>
                <span class="menu-title">Maps</span>
              </a>
              <div class="sub-menu-list">
                <ul>
                  <li class="menu-item">
                    <a href="#">
                      <span class="menu-title">Google maps</span>
                    </a>
                  </li>
                  <li class="menu-item">
                    <a href="#">
                      <span class="menu-title">Open street map</span>
                    </a>
                  </li>
                </ul>
              </div>
            </li>
            <li class="menu-item sub-menu">
              <a href="#">
                <span class="menu-icon">
                  <i class="ri-brush-3-fill"></i>
                </span>
                <span class="menu-title">Theme</span>
              </a>
              <div class="sub-menu-list">
                <ul>
                  <li class="menu-item">
                    <a href="#">
                      <span class="menu-title">Dark</span>
                    </a>
                  </li>
                  <li class="menu-item">
                    <a href="#">
                      <span class="menu-title">Light</span>
                    </a>
                  </li>
                </ul>
              </div>
            </li>
            <li class="menu-item">
              <a href="#">
                <span class="menu-icon">
                  <i class="ri-book-2-fill"></i>
                </span>
                <span class="menu-title">Documentation</span>
              </a>
            </li>
            <li class="menu-item">
              <a href="#">
                <span class="menu-icon">
                  <i class="ri-calendar-fill"></i>
                </span>
                <span class="menu-title">Calendar</span>
              </a>
            </li>
            <li class="menu-item">
              <a href="#">
                <span class="menu-icon">
                  <i class="ri-service-fill"></i>
                </span>
                <span class="menu-title">Examples</span>
              </a>
            </li>
          </ul>
        </nav>
      </div>
      <div class="sidebar-footer"><span>Sidebar footer</span></div>
    </div>
  </aside>
  <div id="overlay" class="overlay"></div>
  <div class="layout">
    <header class="header">
      <a id="btn-collapse" href="#">
        <i class="ri-menu-line ri-xl"></i>
      </a>
      <a id="btn-toggle" href="#" class="sidebar-toggler break-point-lg">
        <i class="ri-menu-line ri-xl"></i>
      </a>
    </header>
    <main class="content">
      <div>
        <h1>Pro Sidebar</h1>
        <p>
          Responsive layout with advanced sidebar menu built with SCSS and vanilla Javascript
        </p>
        <p>
          Full Code and documentation available on  <a href="https://github.com/azouaoui-med/pro-sidebar-template" target="_blank">Github</a>
        </p>
        <div>
          <a href="https://github.com/azouaoui-med/pro-sidebar-template" target="_blank">
            <img alt="GitHub stars" src="https://img.shields.io/github/stars/azouaoui-med/pro-sidebar-template?style=social" />
          </a>
          <a href="https://github.com/azouaoui-med/pro-sidebar-template" target="_blank">
            <img alt="GitHub forks" src="https://img.shields.io/github/forks/azouaoui-med/pro-sidebar-template?style=social" />
          </a>
        </div>
      </div>
      <div>
        <h2>Features</h2>
        <ul>
          <li>Fully responsive</li>
          <li>Collapsable sidebar</li>
          <li>Multi level menu</li>
          <li>RTL support</li>
          <li>Customizable</li>
        </ul>
      </div>
      <div>
        <h2>Resources</h2>
        <ul>
          <li>
            <a target="_blank" href="https://github.com/azouaoui-med/css-pro-layout">
              Css Pro Layout</a>
          </li>
          <li>
            <a target="_blank" href="https://github.com/popperjs/popper-core"> Popper Core</a>
          </li>
          <li>
            <a target="_blank" href="https://remixicon.com/"> Remix Icons</a>
          </li>
        </ul>
      </div>
      <footer class="footer">
        <small style="margin-bottom: 20px; display: inline-block">
          © 2022 made with
          <span style="color: red; font-size: 18px">&#10084;</span> by -
          <a target="_blank" href="https://azouaoui.netlify.com"> Mohamed Azouaoui </a>
        </small>
        <br />
        <div>
          <a href="https://github.com/azouaoui-med" target="_blank" rel="noopener noreferrer">
            <img alt="GitHub followers" src="https://img.shields.io/github/followers/azouaoui-med?label=github&style=social" />
          </a>
          <a href="https://twitter.com/azouaoui_med" target="_blank" rel="noopener noreferrer">
            <img alt="Twitter Follow" src="https://img.shields.io/twitter/follow/azouaoui_med?label=twitter&style=social" />
          </a>
        </div>
      </footer>
    </main>
    <div class="overlay"></div>
  </div>
</div>
$text-color: #b3b8d4;
$secondary-text-color: #dee2ec;

$bg-color: #0c1e35;
$secondary-bg-color: #0b1a2c;

$border-color: rgba(#535d7d, 0.3);

$sidebar-header-height: 64px;
$sidebar-footer-height: 64px;

.layout {
  z-index: 1;
  .header {
    box-shadow: 1px 1px 4px #9aa0b9;
    display: flex;
    align-items: center;
    padding: 20px;
  }
  .content {
    padding: 20px;
    display: flex;
    flex-direction: column;
  }

  .footer {
    text-align: center;
    margin-top: auto;
    margin-bottom: 20px;
    padding: 20px;
  }
  &.rtl {
    .header {
      box-shadow: -1px 1px 4px #9aa0b9;
    }
  }
}

.sidebar {
  color: $text-color;
  overflow-x: hidden !important;
  position: relative;
  background-color: $bg-color;

  .image-wrapper {
    overflow:hidden;
    position: absolute;
    top: 0;
    right: 0;
    bottom: 0;
    left: 0;
    opacity: 0.2;
    z-index: 1;
    display: none;
    > img {
      width: 100%;
      height: 100%;
      object-fit: cover;
      object-position: center;
    }
  }
  &.has-bg-image .image-wrapper {
    display: block;
  }

  .sidebar-layout {
    height: 100%;
    display: flex;
    flex-direction: column;
    position: relative;
    z-index: 2;
    .sidebar-header {
      height: $sidebar-header-height;
      min-height: $sidebar-header-height;
      display: flex;
      align-items: center;
      padding: 0 20px;
      border-bottom: 1px solid $border-color;
      > span {
        overflow: hidden;
        white-space: nowrap;
        text-overflow: ellipsis;
      }
    }
    .sidebar-content {
      flex-grow: 1;
      padding: 10px 0;
    }
    .sidebar-footer {
      height: $sidebar-footer-height;
      min-height: $sidebar-footer-height;
      display: flex;
      align-items: center;
      border-top: 1px solid $border-color;
      padding: 0 20px;
      > span {
        overflow: hidden;
        white-space: nowrap;
        text-overflow: ellipsis;
      }
    }
  }
}

@keyframes swing {
  0%,
  30%,
  50%,
  70%,
  100% {
    transform: rotate(0deg);
  }

  10% {
    transform: rotate(10deg);
  }

  40% {
    transform: rotate(-10deg);
  }

  60% {
    transform: rotate(5deg);
  }

  80% {
    transform: rotate(-5deg);
  }
}

.layout {
  .sidebar {
    .menu {
      ul {
        list-style-type: none;
        padding: 0;
        margin: 0;
      }
      .menu-item {
        a {
          display: flex;
          align-items: center;
          height: 50px;
          padding: 0 20px;
          color: $text-color;

          .menu-icon {
            font-size: 1.2rem;
            width: 35px;
            min-width: 35px;
            height: 35px;
            line-height: 35px;
            text-align: center;
            display: inline-block;
            margin-right: 10px;
            border-radius: 2px;
            transition: color 0.3s;
            i {
              display: inline-block;
            }
          }

          .menu-title {
            font-size: 0.9rem;
            overflow: hidden;
            text-overflow: ellipsis;
            white-space: nowrap;
            flex-grow: 1;
            transition: color 0.3s;
          }
          .menu-prefix,
          .menu-suffix {
            display: inline-block;
            padding: 5px;
            opacity: 1;
            transition: opacity 0.3s;
          }
          &:hover {
            .menu-title {
              color: $secondary-text-color;
            }
            .menu-icon {
              color: $secondary-text-color;
              i {
                animation: swing ease-in-out 0.5s 1 alternate;
              }
            }
            &::after {
              border-color: $secondary-text-color !important;
            }
          }
        }

        &.sub-menu {
          position: relative;
          > a {
            &::after {
              content: "";
              transition: transform 0.3s;
              border-right: 2px solid currentcolor;
              border-bottom: 2px solid currentcolor;
              width: 5px;
              height: 5px;
              transform: rotate(-45deg);
            }
          }

          > .sub-menu-list {
            padding-left: 20px;
            display: none;
            overflow: hidden;
            z-index: 999;
          }
          &.open {
            > a {
              &::after {
                transform: rotate(45deg);
              }
            }
          }
        }

        &.active {
          > a {
            .menu-title {
              color: $secondary-text-color;
            }
            &::after {
              border-color: $secondary-text-color;
            }
            .menu-icon {
              color: $secondary-text-color;
            }
          }
        }
      }
      > ul > .sub-menu > .sub-menu-list {
        background-color: $secondary-bg-color;
      }

      &.icon-shape-circle,
      &.icon-shape-rounded,
      &.icon-shape-square {
        .menu-item a .menu-icon {
          background-color: $secondary-bg-color;
        }
      }

      &.icon-shape-circle .menu-item a .menu-icon {
        border-radius: 50%;
      }
      &.icon-shape-rounded .menu-item a .menu-icon {
        border-radius: 4px;
      }
      &.icon-shape-square .menu-item a .menu-icon {
        border-radius: 0;
      }
    }

    &:not(.collapsed) {
      .menu > ul {
        > .menu-item {
          &.sub-menu {
            > .sub-menu-list {
              visibility: visible !important;
              position: static !important;
              transform: translate(0, 0) !important;
            }
          }
        }
      }
    }

    &.collapsed {
      .menu > ul {
        > .menu-item {
          > a {
            .menu-prefix,
            .menu-suffix {
              opacity: 0;
            }
          }
          &.sub-menu {
            > a {
              &::after {
                content: "";
                width: 5px;
                height: 5px;
                background-color: currentcolor;
                border-radius: 50%;
                display: inline-block;
                position: absolute;
                right: 10px;
                top: 50%;
                border: none;
                transform: translateY(-50%);
              }
              &:hover {
                &::after {
                  background-color: $secondary-text-color;
                }
              }
            }
            > .sub-menu-list {
              transition: none !important;
              width: 200px;
              margin-left: 3px !important;
              border-radius: 4px;
              display: block !important;
            }
          }
          &.active {
            > a {
              &::after {
                background-color: $secondary-text-color;
              }
            }
          }
        }
      }
    }
    &.has-bg-image {
      .menu {
        &.icon-shape-circle,
        &.icon-shape-rounded,
        &.icon-shape-square {
          .menu-item a .menu-icon {
            background-color: rgba($secondary-bg-color, 0.6);
          }
        }
      }
      &:not(.collapsed) {
        .menu {
          > ul > .sub-menu > .sub-menu-list {
            background-color: rgba($secondary-bg-color, 0.6);
          }
        }
      }
    }
  }

  &.rtl {
    .sidebar {
      .menu {
        .menu-item {
          a {
            .menu-icon {
              margin-left: 10px;
              margin-right: 0;
            }
          }

          &.sub-menu {
            > a {
              &::after {
                transform: rotate(135deg);
              }
            }

            > .sub-menu-list {
              padding-left: 0;
              padding-right: 20px;
            }
            &.open {
              > a {
                &::after {
                  transform: rotate(45deg);
                }
              }
            }
          }
        }
      }

      &.collapsed {
        .menu > ul {
          > .menu-item {
            &.sub-menu {
              a::after {
                right: auto;
                left: 10px;
              }

              > .sub-menu-list {
                margin-left: -3px !important;
              }
            }
          }
        }
      }
    }
  }
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  height: 100vh;
  font-family: "Roboto", sans-serif;
  color: #212529;
}

a {
  text-decoration: none;
}

@media (max-width: 992px) {
  #btn-collapse {
    display: none;
  }
}
View Compiled
const ANIMATION_DURATION = 300;

const SIDEBAR_EL = document.getElementById("sidebar");

const SUB_MENU_ELS = document.querySelectorAll(
  ".menu > ul > .menu-item.sub-menu"
);

const FIRST_SUB_MENUS_BTN = document.querySelectorAll(
  ".menu > ul > .menu-item.sub-menu > a"
);

const INNER_SUB_MENUS_BTN = document.querySelectorAll(
  ".menu > ul > .menu-item.sub-menu .menu-item.sub-menu > a"
);

class PopperObject {
  instance = null;
  reference = null;
  popperTarget = null;

  constructor(reference, popperTarget) {
    this.init(reference, popperTarget);
  }

  init(reference, popperTarget) {
    this.reference = reference;
    this.popperTarget = popperTarget;
    this.instance = Popper.createPopper(this.reference, this.popperTarget, {
      placement: "right",
      strategy: "fixed",
      resize: true,
      modifiers: [
        {
          name: "computeStyles",
          options: {
            adaptive: false
          }
        },
        {
          name: "flip",
          options: {
            fallbackPlacements: ["left", "right"]
          }
        }
      ]
    });

    document.addEventListener(
      "click",
      (e) => this.clicker(e, this.popperTarget, this.reference),
      false
    );

    const ro = new ResizeObserver(() => {
      this.instance.update();
    });

    ro.observe(this.popperTarget);
    ro.observe(this.reference);
  }

  clicker(event, popperTarget, reference) {
    if (
      SIDEBAR_EL.classList.contains("collapsed") &&
      !popperTarget.contains(event.target) &&
      !reference.contains(event.target)
    ) {
      this.hide();
    }
  }

  hide() {
    this.instance.state.elements.popper.style.visibility = "hidden";
  }
}

class Poppers {
  subMenuPoppers = [];

  constructor() {
    this.init();
  }

  init() {
    SUB_MENU_ELS.forEach((element) => {
      this.subMenuPoppers.push(
        new PopperObject(element, element.lastElementChild)
      );
      this.closePoppers();
    });
  }

  togglePopper(target) {
    if (window.getComputedStyle(target).visibility === "hidden")
      target.style.visibility = "visible";
    else target.style.visibility = "hidden";
  }

  updatePoppers() {
    this.subMenuPoppers.forEach((element) => {
      element.instance.state.elements.popper.style.display = "none";
      element.instance.update();
    });
  }

  closePoppers() {
    this.subMenuPoppers.forEach((element) => {
      element.hide();
    });
  }
}

const slideUp = (target, duration = ANIMATION_DURATION) => {
  const { parentElement } = target;
  parentElement.classList.remove("open");
  target.style.transitionProperty = "height, margin, padding";
  target.style.transitionDuration = `${duration}ms`;
  target.style.boxSizing = "border-box";
  target.style.height = `${target.offsetHeight}px`;
  target.offsetHeight;
  target.style.overflow = "hidden";
  target.style.height = 0;
  target.style.paddingTop = 0;
  target.style.paddingBottom = 0;
  target.style.marginTop = 0;
  target.style.marginBottom = 0;
  window.setTimeout(() => {
    target.style.display = "none";
    target.style.removeProperty("height");
    target.style.removeProperty("padding-top");
    target.style.removeProperty("padding-bottom");
    target.style.removeProperty("margin-top");
    target.style.removeProperty("margin-bottom");
    target.style.removeProperty("overflow");
    target.style.removeProperty("transition-duration");
    target.style.removeProperty("transition-property");
  }, duration);
};
const slideDown = (target, duration = ANIMATION_DURATION) => {
  const { parentElement } = target;
  parentElement.classList.add("open");
  target.style.removeProperty("display");
  let { display } = window.getComputedStyle(target);
  if (display === "none") display = "block";
  target.style.display = display;
  const height = target.offsetHeight;
  target.style.overflow = "hidden";
  target.style.height = 0;
  target.style.paddingTop = 0;
  target.style.paddingBottom = 0;
  target.style.marginTop = 0;
  target.style.marginBottom = 0;
  target.offsetHeight;
  target.style.boxSizing = "border-box";
  target.style.transitionProperty = "height, margin, padding";
  target.style.transitionDuration = `${duration}ms`;
  target.style.height = `${height}px`;
  target.style.removeProperty("padding-top");
  target.style.removeProperty("padding-bottom");
  target.style.removeProperty("margin-top");
  target.style.removeProperty("margin-bottom");
  window.setTimeout(() => {
    target.style.removeProperty("height");
    target.style.removeProperty("overflow");
    target.style.removeProperty("transition-duration");
    target.style.removeProperty("transition-property");
  }, duration);
};

const slideToggle = (target, duration = ANIMATION_DURATION) => {
  if (window.getComputedStyle(target).display === "none")
    return slideDown(target, duration);
  return slideUp(target, duration);
};

const PoppersInstance = new Poppers();

/**
 * wait for the current animation to finish and update poppers position
 */
const updatePoppersTimeout = () => {
  setTimeout(() => {
    PoppersInstance.updatePoppers();
  }, ANIMATION_DURATION);
};

/**
 * sidebar collapse handler
 */
document.getElementById("btn-collapse").addEventListener("click", () => {
  SIDEBAR_EL.classList.toggle("collapsed");
  PoppersInstance.closePoppers();
  if (SIDEBAR_EL.classList.contains("collapsed"))
    FIRST_SUB_MENUS_BTN.forEach((element) => {
      element.parentElement.classList.remove("open");
    });

  updatePoppersTimeout();
});

/**
 * sidebar toggle handler (on break point )
 */
document.getElementById("btn-toggle").addEventListener("click", () => {
  SIDEBAR_EL.classList.toggle("toggled");

  updatePoppersTimeout();
});

/**
 * toggle sidebar on overlay click
 */
document.getElementById("overlay").addEventListener("click", () => {
  SIDEBAR_EL.classList.toggle("toggled");
});

const defaultOpenMenus = document.querySelectorAll(".menu-item.sub-menu.open");

defaultOpenMenus.forEach((element) => {
  element.lastElementChild.style.display = "block";
});

/**
 * handle top level submenu click
 */
FIRST_SUB_MENUS_BTN.forEach((element) => {
  element.addEventListener("click", () => {
    if (SIDEBAR_EL.classList.contains("collapsed"))
      PoppersInstance.togglePopper(element.nextElementSibling);
    else {
      const parentMenu = element.closest(".menu.open-current-submenu");
      if (parentMenu)
        parentMenu
          .querySelectorAll(":scope > ul > .menu-item.sub-menu > a")
          .forEach(
            (el) =>
              window.getComputedStyle(el.nextElementSibling).display !==
                "none" && slideUp(el.nextElementSibling)
          );
      slideToggle(element.nextElementSibling);
    }
  });
});

/**
 * handle inner submenu click
 */
INNER_SUB_MENUS_BTN.forEach((element) => {
  element.addEventListener("click", () => {
    slideToggle(element.nextElementSibling);
  });
});
View Compiled

External CSS

  1. https://unpkg.com/css-pro-layout@1.1.0/dist/css/css-pro-layout.css
  2. https://cdn.jsdelivr.net/npm/remixicon@2.2.0/fonts/remixicon.css

External JavaScript

  1. https://unpkg.com/@popperjs/core@2