Dropdown Menu

Toppings 
<details
  class="dropdownMenu dropdownMenuSelections flow__inline position__relative"
>
  <summary
    class="border__all color__bg--contrast color__border--base--light flow__inline flow__align--block-center flow__gap--s padding__inline--m radius__s"
  >
    <span class="type__size--m-l--fluid">Toppings</span>
    <svg
      xmlns="http://www.w3.org/2000/svg"
      fill="none"
      viewBox="0 0 24 24"
      stroke="currentColor"
    >
      <path
        stroke-linecap="round"
        stroke-linejoin="round"
        d="m19.5 8.25-7.5 7.5-7.5-7.5"
      ></path>
    </svg>
  </summary>
  <section
    class="border__all color__bg--contrast--adaptive color__border--base--light flow__grid overflow__hidden position__absolute radius__s shadow"
  >
    <button
      class="selected border__bottom color__border--base--light color__type--base flow__flex flow__align--block-center flow__align--inline-between flow__gap--s padding__inline--m"
    >
      <span class="type__size--m-l--fluid">Cherries</span>
      <svg
        xmlns="http://www.w3.org/2000/svg"
        fill="none"
        viewBox="0 0 24 24"
        stroke="currentColor"
      >
        <path
          stroke-linecap="round"
          stroke-linejoin="round"
          d="m4.5 12.75 6 6 9-13.5"
        ></path>
      </svg>
    </button>
    <button
      class="border__bottom color__border--base--light color__type--base flow__flex flow__align--block-center flow__align--inline-between flow__gap--s padding__inline--m"
    >
      <span class="type__size--m-l--fluid">Sprinkles</span>
      <svg
        xmlns="http://www.w3.org/2000/svg"
        fill="none"
        viewBox="0 0 24 24"
        stroke="currentColor"
      >
        <path
          stroke-linecap="round"
          stroke-linejoin="round"
          d="m4.5 12.75 6 6 9-13.5"
        ></path>
      </svg>
    </button>
    <button
      class="border__bottom color__border--base--light color__type--base flow__flex flow__align--block-center flow__align--inline-between flow__gap--s padding__inline--m"
    >
      <span class="type__size--m-l--fluid">Whip Cream</span>
      <svg
        xmlns="http://www.w3.org/2000/svg"
        fill="none"
        viewBox="0 0 24 24"
        stroke="currentColor"
      >
        <path
          stroke-linecap="round"
          stroke-linejoin="round"
          d="m4.5 12.75 6 6 9-13.5"
        ></path>
      </svg>
    </button>
  </section>
</details>
.dropdownMenu {
  --elementHeight: var(--size__xl);

  > summary {
    block-size: var(--elementHeight);
    cursor: pointer;
    user-select: none;

    svg {
      color: var(--color__base--mid);
    }
  }

  &[open] > summary {
    border-color: var(--color__base--semi);
  }

  /* Bringing in sizing/stroke styling to CSS */
  svg {
    block-size: 1.625cap;
    stroke-width: 3;
  }

  > section {
    --block-end: calc(var(--size__xs) * -1);
    --inline-start: 50%;
    inline-size: 12.5rem;
    /* Centers the menu relative to the button */
    transform: translate(-50%, 100%);

    button {
      --outline__offset: calc(var(--size__xs) * -1);
      background: unset;
      block-size: var(--elementHeight);
      border-left: unset;
      border-right: unset;
      border-top: unset;
      text-align: unset;
      /* Baby transition */
      transition: background-color 0.375s ease-in;

      &:focus,
      &:hover {
        background-color: var(--color__highlight--ghost);
      }

      /* Last item is border-less */
      &:last-child {
        border-bottom: unset;
      }

      svg {
        color: var(--color__highlight);
        opacity: 0;
        /* Baby transition */
        transition: opacity 0.1875s ease-in;
      }

      &.selected svg {
        opacity: 1;
      }
    }
  }
}
const queryDropdownMenus = () => {
  const dropdownMenus = document.querySelectorAll(".dropdownMenu");
  dropdownMenus.forEach((dropdownMenu) => {
    const dropdownMenuSummary = dropdownMenu.querySelector("summary");
    const dropdownMenuButtons = dropdownMenu.querySelectorAll("button");
    dropdownMenu.addEventListener("toggle", (e) => {
      // Focus on the first selected button
      const selectedButton = document.querySelector(".selected");
      selectedButton?.focus();

      // Only attach events IF the `details` is actually open
      if (dropdownMenu.open) {
        document.addEventListener(
          "click",
          (e) => {
            // Only toggle `open` if my click is outside the menu
            if (!dropdownMenu.contains(e.target)) {
              dropdownMenu.removeAttribute("open");
            }
          },
          false
        );

        document.addEventListener("keydown", (e) => {
          // Escape closes the menu
          if (e.key === "Escape") {
            dropdownMenu.removeAttribute("open");
          }

          // If I tab forward and reach the last element
          if (
            e.key === "Tab" &&
            !(e.shiftKey && e.key === "Tab") &&
            document.activeElement === [...dropdownMenuButtons].pop()
          ) {
            dropdownMenu.removeAttribute("open");
          }

          // If I tab backwards and reach the first element or am
          // currently focused on the `summary` element.
          if (
            e.shiftKey &&
            e.key === "Tab" &&
            (document.activeElement === [...dropdownMenuButtons].shift() ||
              document.activeElement === dropdownMenu.querySelector("summary"))
          ) {
            dropdownMenu.removeAttribute("open");
          }
        });
      } else {
        // Cleanup my listeners before the `toggle` event is
        document.removeEventListener("click", () => null);
        document.removeEventListener("keydown", () => null);
      }
    });
  });
};

const queryDropdownMenuSelections = () => {
  const dropdownMenus = document.querySelectorAll(
    ".dropdownMenuSelections, .dropdownMenuSelect"
  );
  dropdownMenus.forEach((dropdownMenu) => {
    const dropdownMenuButtons = dropdownMenu.querySelectorAll("button");

    // Toggles the clicked button to have the `.selected` class
    dropdownMenuButtons.forEach((button) => {
      button.addEventListener("click", (e) => {
        e.currentTarget.classList.toggle("selected");
      });
    });
  });
};

// This function is is you want to implement a single selection
const queryDropdownMenuSelect = () => {
  const dropdownMenus = document.querySelectorAll(".dropdownMenuSelect");

  dropdownMenus.forEach((dropdownMenu) => {
    const dropdownMenuSummary = dropdownMenu.querySelector("summary");
    const dropdownMenuButtons = dropdownMenu.querySelectorAll("button");

    dropdownMenuButtons.forEach((button) => {
      button.addEventListener("click", (e) => {
        // Update the selection label
        const label = dropdownMenuSummary.querySelector("span");
        label.textContent = e.srcElement.innerText;

        // Remove all other `.selected` classes
        [...dropdownMenuButtons]
          .filter((item) => item !== e.currentTarget)
          .map((item) => item.classList.remove("selected"));

        // Close the dropdown
        dropdownMenu.removeAttribute("open");
      });
    });
  });
};

Highlights

For this demo I utilized the details element primarily because you get the open/close paradigm of this type of control for free without having to manage state via Javascript. I also love the association that this is basically an accordion type of element. I’m also using the great Feather library for the icons throughout the demos.

I also find it really interesting that with this type of control you can put whatever you want inside the menu and the overall behavior is maintained. For example, in this demo we are utilizing buttons to represent menu items and listening for a click event to make the SVG visible. You could easily reach a checkbox or radio or just as easily turn it into a link of anchor tags to provide a nav menu.

I was recently reminded of the awesomeness of the cap unit for sizing SVGs for icon use, to find a great balance for icons aligned to adjacent text. I am also setting the stroke-width for the SVG in the CSS to make it a bit easier to tweak:

svg {
  block-size: 1.625cap;
  stroke-width: 3;
}

Adding the Selected State

By adding a click event listener to the buttons in the menu, we can toggle the respected state:

const dropdownMenu = document.querySelector(".dropdownMenu");
const dropdownMenuButtons = dropdownMenu.querySelectorAll("button");

dropdownMenuButtons.forEach((button) => {
  button.addEventListener("click", (e) => {
    // Remove selection from all the other buttons
    [...dropdownMenuButtons]
      .filter((item) => item !== e.currentTarget)
      .map((item) => item.classList.remove("selected"));
    // Only apply it to my current selection
    e.currentTarget.classList.toggle("selected");
  });
});

Clicking Outside + Focus Events

I love that details has the ability to open/close the associated hidden block of content (i.e. anything not in summary) when you click the summary, but using this element to display a menu has some associated expectations that don’t come for free and need to be supplied via Javascript, in particular:

const dropdownMenu = document.querySelector(".dropdownMenu");
const dropdownMenuSummary = dropdownMenu.querySelector("summary");
const dropdownMenuButtons = dropdownMenu.querySelectorAll("button");

dropdownMenu.addEventListener("toggle", (e) => {
  // Focus on the first selected button
  const selectedButton = document.querySelector(".selected");
  selectedButton?.focus();

  // Only attach events IF the `details` is actually open
  if (dropdownMenu.open) {
    document.addEventListener(
      "click",
      (e) => {
        // Only toggle `open` if my click is outside the menu
        if (!dropdownMenu.contains(e.target)) {
          dropdownMenu.removeAttribute("open");
        }
      },
      false
    );

    document.addEventListener("keydown", (e) => {
      // Escape closes the menu
      if (e.key === "Escape") {
        dropdownMenu.removeAttribute("open");
      }

      // If I tab forward and reach the last element
      if (
        e.key === "Tab" &&
        !(e.shiftKey && e.key === "Tab") &&
        document.activeElement === [...dropdownMenuButtons].pop()
      ) {
        dropdownMenu.removeAttribute("open");
      }

      // If I tab backwards and reach the first element or am
      // currently focused on the `summary` element.
      if (
        e.shiftKey &&
        e.key === "Tab" &&
        (document.activeElement === [...dropdownMenuButtons].shift() ||
          document.activeElement === dropdownMenu.querySelector("summary"))
      ) {
        dropdownMenu.removeAttribute("open");
      }
    });
  } else {
    // Cleanup my listeners before the `toggle` event is
    document.removeEventListener("click", () => null);
    document.removeEventListener("keydown", () => null);
  }
});

Alternates

Interfaces Pasta

Here’s an example of a list of links presented inside a Dropdown Menu.

Ascending

Here’s a more straight forward implementation of the initial demo, but behaves more like a select (i.e. making a single selection closes the menu).