Accessible Dropdown Menu With Smooth JavaScript Animations

The DropdownMenu JavaScript class provides a simple way to create customizable, accessible dropdown menus with smooth animations on your webpage.

Built with TypeScript/Vanilla JavaScript, CSS/CSS3, and plain HTML buttons, this JS dropdown solution avoids relying on the <select> element for a truly custom look and feel.

Features:

• Smooth animations for opening and closing the menu
• Keyboard accessibility for navigation
• Click outside to close functionality
• Customizable options and styling
• Responsive design with dark mode support

How to use it:

1. Create the basic HTML structure for the dropdown menu. This involves nesting buttons and divs to represent the menu and its items:

<main>
  <div class="drop" id="myDropdown">
    <button class="drop__btn" aria-expanded="false" aria-haspopup="true" type="button"></button>
    <div class="drop__items" data-items>
      <div class="drop__items-inner">
        <button class="drop__btn" type="button" value="javascript">JavaScript</button>
        <button class="drop__btn" type="button" value="css">CSS/CSS3</button>
        <button class="drop__btn" type="button" value="html">HTML5</button>
      </div>
    </div>
  </div>
</main>

2. Copy and paste the following CSS styles into your stylesheet. You can customize colors, fonts, and animations by modifying the CSS variables:

* {
  border: 0;
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}
:root {
  --hue: 223;
  --bg: hsl(0,0%,100%);
  --fg: hsl(var(--hue),10%,10%);
  --trans-dur: 0.3s;
  --trans-ease-in-out: cubic-bezier(0.65,0,0.35,1);
  --trans-ease-out: cubic-bezier(0.33,1,0.68,1);
  font-size: calc(20px + (40 - 20) * (100vw - 280px) / (3840 - 280));
}
button {
  color: var(--fg);
  font: 1em/1.5;
  transition: background-color var(--trans-dur), color var(--trans-dur);
}
main {
  margin: auto;
  padding: 0.75em 0;
  width: min-content;
  height: 12em;
}
.drop {
  --drop-trans-dur: 0.5s;
  --drop-flare-dist: 0;
  border-radius: 0.5em;
  margin: auto;
  padding: 0.25em 0.25em 0 0.25em;
  position: relative;
  min-width: 9em;
}
.drop, .drop:after {
  background-color: hsl(var(--hue), 10%, 90%);
  transition: background-color var(--trans-dur);
}
.drop:before, .drop:after {
  content: "";
  position: absolute;
}
.drop:before {
  background-image: radial-gradient(100% 100% at 100% 50%, hsla(var(--hue), 90%, 50%, 0.5), hsla(var(--hue), 90%, 50%, 0) 50%);
  display: none;
  right: 0;
  bottom: 100%;
  width: 9em;
  height: 9em;
}
.drop:after {
  border-radius: 0.4375em;
  display: block;
  top: 0.125em;
  left: 0.125em;
  width: calc(100% - 0.25em);
  height: calc(100% - 0.25em);
}
.drop__btn {
  background-color: white;
  border-radius: 0.375em;
  box-shadow: 0 0 0 0.25em hsla(var(--hue), 90%, 50%, 0);
  cursor: pointer;
  display: flex;
  align-items: center;
  line-height: 1;
  height: 2.5em;
  outline: transparent;
  margin-bottom: 0.25em;
  padding: 0.75em;
  position: relative;
  width: 100%;
  transition: background-color var(--trans-dur), box-shadow calc(var(--trans-dur) / 2) var(--trans-ease-in-out), color var(--drop-trans-dur);
  -webkit-appearance: none;
  appearance: none;
  -webkit-tap-highlight-color: transparent;
  z-index: 1;
}
.drop__btn:hover, .drop__btn:focus-visible, .drop__btn[aria-expanded=true] {
  background-color: hsl(var(--hue), 10%, 95%);
}
.drop__btn:focus-visible {
  box-shadow: 0 0 0 0.25em hsla(var(--hue), 90%, 50%, 1);
}
.drop__btn:after {
  border-top: 0.375em solid currentColor;
  border-right: 0.375em solid transparent;
  border-left: 0.375em solid transparent;
  content: "";
  display: block;
  margin-inline-start: auto;
  width: 0;
  height: 0;
  transform-origin: 50% 37.5%;
  transition: transform var(--drop-trans-dur) var(--trans-ease-out);
}
.drop__btn[aria-expanded=true]:after {
  transform: rotate(0.5turn);
}
.drop--collapsing, .drop--expanding, .drop__items {
  overflow: hidden;
}
.drop__items {
  height: 0;
}
.drop__items-inner {
  visibility: hidden;
}
.drop--collapsing .drop__btn[aria-expanded=true] {
  background-color: white;
}
.drop--collapsing .drop__btn[aria-expanded=true]:after {
  transform: rotate(0);
}
.drop--expanding:before {
  display: block;
}
.drop__items .drop__btn:hover, .drop__items .drop__btn:focus-visible {
  background-color: hsl(var(--hue), 10%, 97.5%);
  color: hsla(var(--hue), 90%, 50%);
}
.drop__items .drop__btn:focus-visible {
  box-shadow: 0 0 0 0.25em hsla(var(--hue), 90%, 50%, 0);
}
.drop__items .drop__btn:after {
  border: 0;
  content: "✓";
  display: none;
  width: auto;
  height: auto;
}
.drop__items .drop__btn--selected:after {
  display: block;
}
.drop__btn[aria-expanded=true] ~ .drop__items {
  height: auto;
}
.drop__btn[aria-expanded=true] ~ .drop__items .drop__items-inner {
  visibility: visible;
}
.drop:has([aria-expanded=true]) {
  height: auto;
}
.drop:has([aria-expanded=true]):before {
  transform: translateY(calc(9em + var(--drop-flare-dist)));
  transition: transform var(--drop-trans-dur) linear;
}
/* Dark theme */
@media (prefers-color-scheme: dark) {
  :root {
    --bg: hsl(var(--hue),10%,10%);
    --fg: hsl(var(--hue),10%,90%);
  }
  .drop, .drop:after {
    background-color: black;
  }
  .drop__btn {
    background-color: hsl(var(--hue), 10%, 10%);
  }
  .drop__btn:hover, .drop__btn:focus-visible, .drop__btn[aria-expanded=true] {
    background-color: hsl(var(--hue), 10%, 20%);
  }
  .drop__items .drop__btn:hover, .drop__items .drop__btn:focus-visible {
    background-color: hsl(var(--hue), 10%, 15%);
    color: hsla(var(--hue), 90%, 70%);
  }
  .drop--collapsing .drop__btn[aria-expanded=true] {
    background-color: hsl(var(--hue), 10%, 10%);
  }
}

3. The JavaScript portion handles the menu’s dynamic behavior. It manages the opening and closing animations, keyboard navigation, and option selection. Copy and include the following JavaScript code in your project:

class DropdownMenu {
    /**
     * @param el CSS selector of the menu
    */
    constructor(el) {
        var _a, _b, _c;
        /** Animation objects */
        this.animations = [];
        /** Options for this menu */
        this.options = [
            // OVERRIDE YOUR MENU ITEMS HERE
            { name: "javascript", friendlyName: "JavaScript" },
            { name: "css", friendlyName: "CSS/CSS3" },
            { name: "html", friendlyName: "HTML5" }
        ];
        /** Selected option by name */
        this.selected = "javascript";
        /** Menu is collapsing */
        this.isCollapsing = false;
        /** Menu is expanding */
        this.isExpanding = false;
        /** Actions to run after collapsing the item. */
        this.animActionsCollapse = {
            onfinish: this.onAnimationFinish.bind(this, false),
            oncancel: () => { this.isCollapsing = false; }
        };
        /** Actions to run after expanding the item. */
        this.animActionsExpand = {
            onfinish: this.onAnimationFinish.bind(this, true),
            oncancel: () => { this.isExpanding = false; }
        };
        this.el = document.querySelector(el);
        this.menuButton = (_a = this.el) === null || _a === void 0 ? void 0 : _a.querySelector("button");
        this.itemList = (_b = this.el) === null || _b === void 0 ? void 0 : _b.querySelector("[data-items]");
        this.defaultOption();
        document.addEventListener("click", this.outsideToClose.bind(this));
        window.addEventListener("keydown", this.escToClose.bind(this));
        (_c = this.el) === null || _c === void 0 ? void 0 : _c.addEventListener("click", this.toggle.bind(this));
        window.addEventListener("keydown", this.kbdAction.bind(this));
    }
    /** Transition duration specific to the menu */
    get transDuration() {
        if (this.el) {
            const style = getComputedStyle(this.el);
            const rawDur = style.getPropertyValue("--drop-trans-dur");
            let dur = rawDur.substring(0, rawDur.indexOf("s"));
            const mIndex = dur.indexOf("m");
            if (mIndex > -1) {
                dur = dur.substring(0, mIndex);
                return +dur;
            }
            // seconds to milliseconds
            return +dur * 1e3;
        }
        return 0;
    }
    /** Display the default selected option. */
    defaultOption() {
        var _a;
        const buttonEl = (_a = this.itemList) === null || _a === void 0 ? void 0 : _a.querySelector(`[value="${this.selected}"]`);
        buttonEl === null || buttonEl === void 0 ? void 0 : buttonEl.classList.add("drop__btn--selected");
        if (this.menuButton) {
            const optionFound = this.options.find(option => option.name === this.selected);
            this.menuButton.textContent = (optionFound === null || optionFound === void 0 ? void 0 : optionFound.friendlyName) || "";
        }
    }
    /**
     * Navigate the menu options with arrow keys.
     * @param e Keydown event
     */
    kbdAction(e) {
        var _a;
        const { key } = e;
        const tabOrArrow = key === "Tab" || key === "ArrowUp" || key === "ArrowDown";
        const notAnimating = !this.isExpanding && !this.isCollapsing;
        if (notAnimating && ((_a = this.menuButton) === null || _a === void 0 ? void 0 : _a.ariaExpanded) === "true" && tabOrArrow) {
            this.navigateOption(e);
        }
    }
    /**
     * Press Esc to close the menu.
     * @param e Keydown event
     */
    escToClose(e) {
        var _a;
        if (e.key === "Escape" && (!this.isCollapsing && ((_a = this.menuButton) === null || _a === void 0 ? void 0 : _a.ariaExpanded) === "true")) {
            this.toggle(e);
        }
    }
    /**
     * Click outside the menu to close.
     * @param e Click event
     */
    outsideToClose(e) {
        var _a;
        let target = e.target;
        let elFound = false;
        if (!this.isCollapsing && ((_a = this.menuButton) === null || _a === void 0 ? void 0 : _a.ariaExpanded) === "true") {
            do {
                target = target.parentElement;
                if (target === this.el) {
                    elFound = true;
                }
            } while (target);
            if (!elFound) {
                this.toggle(e);
            }
        }
    }
    /**
     * Navigate the menu options with arrow keys.
     * @param e Keydown event
     */
    navigateOption(e) {
        var _a;
        const itemList = (_a = this.el) === null || _a === void 0 ? void 0 : _a.querySelector("[data-items]");
        const buttonEls = itemList === null || itemList === void 0 ? void 0 : itemList.querySelectorAll("button");
        const buttons = Array.from(buttonEls || []);
        const buttonsTemp = [...buttons]; // for getting the first and last
        const first = buttonsTemp.shift();
        const last = buttonsTemp.pop();
        const currentItem = document.activeElement;
        const { key, shiftKey } = e;
        const downKey = key === "ArrowDown";
        const upKey = key === "ArrowUp";
        const currentIndex = buttons.indexOf(currentItem);
        if (!buttons.length) {
            // do nothing for no items
            e.preventDefault();
        }
        else if (downKey) {
            // next item, go to the first if on the last
            e.preventDefault();
            const nextIndex = currentIndex + 1;
            if (nextIndex >= buttons.length) {
                first === null || first === void 0 ? void 0 : first.focus();
                return;
            }
            buttons[nextIndex].focus();
        }
        else if (upKey) {
            // previous item, go to the last if on the first
            e.preventDefault();
            const prevIndex = currentIndex - 1;
            if (prevIndex < 0) {
                last === null || last === void 0 ? void 0 : last.focus();
                return;
            }
            buttons[prevIndex].focus();
        }
        else if (buttons.length === 1 || ((!(itemList === null || itemList === void 0 ? void 0 : itemList.contains(currentItem)) || currentItem === last) && !shiftKey)) {
            // go to the first item if on the last
            e.preventDefault();
            first === null || first === void 0 ? void 0 : first.focus();
        }
        else if ((!(itemList === null || itemList === void 0 ? void 0 : itemList.contains(currentItem)) || currentItem === first) && shiftKey) {
            // go to the last item if on the first
            e.preventDefault();
            last === null || last === void 0 ? void 0 : last.focus();
        }
    }
    /**
     * Open or close the menu.
     * @param e Click event
     */
    toggle(e) {
        var _a, _b;
        e.preventDefault();
        (_a = this.el) === null || _a === void 0 ? void 0 : _a.classList.remove("drop--collapsing", "drop--expanding");
        const shouldExpand = ((_b = this.menuButton) === null || _b === void 0 ? void 0 : _b.ariaExpanded) === "true";
        if (this.isCollapsing || !shouldExpand) {
            this.expand();
        }
        else if (this.isExpanding || shouldExpand) {
            this.collapse(e);
        }
    }
    /** Expand the menu. */
    expand() {
        var _a, _b;
        if (!this.el || !this.itemList)
            return;
        this.itemList.style.height = `${this.itemList.offsetHeight}px`;
        (_a = this.menuButton) === null || _a === void 0 ? void 0 : _a.setAttribute("aria-expanded", "true");
        this.el.classList.add("drop--expanding");
        this.isExpanding = true;
        // reset the animations
        this.animations.forEach(anim => anim.cancel());
        this.animations = [];
        const buttonEls = this.itemList.querySelectorAll("button");
        const buttons = Array.from(buttonEls || []);
        // animate the menu height
        const startHeight = this.itemList.offsetHeight || 0;
        const endHeight = ((_b = this.itemList.firstElementChild) === null || _b === void 0 ? void 0 : _b.offsetHeight) || 0;
        const itemListAnim = this.itemList.animate({ height: [`${startHeight}px`, `${endHeight}px`] }, {
            duration: this.transDuration,
            easing: "cubic-bezier(0.33,1,0.68,1.33)"
        });
        itemListAnim.onfinish = this.animActionsExpand.onfinish;
        itemListAnim.oncancel = this.animActionsExpand.oncancel;
        this.animations.push(itemListAnim);
        // animate the buttons
        buttons.forEach((button, i) => {
            // animate the buttons
            const buttomAnim = button.animate({ transform: ["translateY(100%)", "translateY(0)"] }, {
                duration: this.transDuration,
                delay: this.transDuration / 12 * i,
                easing: "cubic-bezier(0.33,1,0.68,1)"
            });
            this.animations.push(buttomAnim);
        });
        // animate the flare
        this.el.style.setProperty("--drop-flare-dist", `${endHeight}px`);
    }
    /**
     * Collapse the menu.
     * @param e Click event
     */
    collapse(e) {
        var _a, _b, _c;
        if (!this.el || !this.itemList)
            return;
        this.el.classList.add("drop--collapsing");
        this.isCollapsing = true;
        // reset the animations
        this.animations.forEach(anim => anim.cancel());
        this.animations = [];
        const clickedButton = e.target;
        const buttonEls = (_a = this.itemList) === null || _a === void 0 ? void 0 : _a.querySelectorAll("button");
        const buttons = Array.from(buttonEls || []);
        // animate the menu height
        const startHeight = ((_b = this.itemList) === null || _b === void 0 ? void 0 : _b.offsetHeight) || 0;
        const endHeight = 0;
        const easing = "cubic-bezier(0.33,1,0.68,1)";
        const itemListAnim = this.itemList.animate({ height: [`${startHeight}px`, `${endHeight}px`] }, { duration: this.transDuration, easing });
        itemListAnim.onfinish = this.animActionsCollapse.onfinish;
        itemListAnim.oncancel = this.animActionsCollapse.oncancel;
        this.animations.push(itemListAnim);
        // animate the buttons
        buttons.forEach((button, i) => {
            if (clickedButton.value) {
                // remove the previous checkmark after selecting an option
                button.classList.remove("drop__btn--selected");
            }
            // animate the buttons
            const delayInc = this.transDuration / 12;
            const buttomAnim = button.animate({ transform: ["translateY(0)", "translateY(100%)"] }, {
                duration: this.transDuration,
                delay: delayInc * (buttons.length - 1) - (delayInc * i),
                easing
            });
            this.animations.push(buttomAnim);
        });
        if (clickedButton.value) {
            // set this menu’s option from a `value`
            clickedButton.classList.add("drop__btn--selected");
            if (this.menuButton) {
                const optionFound = this.options.find(option => option.name === clickedButton.value);
                this.menuButton.textContent = (optionFound === null || optionFound === void 0 ? void 0 : optionFound.friendlyName) || "";
            }
        }
        (_c = this.menuButton) === null || _c === void 0 ? void 0 : _c.focus();
        // animate the flare
        this.el.style.setProperty("--drop-flare-dist", `${endHeight}px`);
    }
    /**
     * Actions to run when the animation is finished
     * @param open Menu should be expanded
     */
    onAnimationFinish(open) {
        var _a, _b;
        if (!this.el || !this.itemList)
            return;
        (_a = this.menuButton) === null || _a === void 0 ? void 0 : _a.setAttribute("aria-expanded", `${open}`);
        this.animations = [];
        this.isCollapsing = false;
        this.isExpanding = false;
        this.itemList.style.height = "";
        (_b = this.el) === null || _b === void 0 ? void 0 : _b.classList.remove("drop--collapsing", "drop--expanding");
    }
}

4. Initialize the dropdown menu by creating a new instance of the DropdownMenu class and targeting the appropriate HTML element:

window.addEventListener("DOMContentLoaded", () => {
  const drop = new DropdownMenu("#myDropdown");
});