UI 组件困难

ARIA Combobox

Accessible combobox autocomplete implementing ARIA 1.2 combobox pattern with keyboard navigation and screen reader support.

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vanilla-js css

目标: JS HTML

代码

*,
*::before,
*::after {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

body {
  font-family: "Inter", system-ui, -apple-system, sans-serif;
  background: #0a0a0a;
  color: #e4e4e7;
  line-height: 1.6;
  min-height: 100vh;
}

.demo {
  max-width: 640px;
  margin: 0 auto;
  padding: 3rem 1.5rem;
}

.demo-title {
  font-size: 1.75rem;
  font-weight: 700;
  color: #fafafa;
  letter-spacing: -0.02em;
}

.demo-sub {
  color: #a1a1aa;
  margin-top: 0.25rem;
  font-size: 0.95rem;
}

/* Combobox */
.combobox-section {
  margin-top: 2rem;
  background: #111113;
  border: 1px solid #27272a;
  border-radius: 12px;
  padding: 1.5rem;
}

.combobox-container {
  position: relative;
}

.combobox-label {
  display: block;
  font-size: 0.85rem;
  font-weight: 500;
  color: #a1a1aa;
  margin-bottom: 0.5rem;
}

.combobox-wrapper {
  position: relative;
}

.combobox-input-wrap {
  position: relative;
  display: flex;
  align-items: center;
}

.combobox-search-icon {
  position: absolute;
  left: 0.85rem;
  color: #52525b;
  pointer-events: none;
}

.combobox-input {
  width: 100%;
  padding: 0.7rem 2.5rem 0.7rem 2.5rem;
  background: #09090b;
  border: 1px solid #27272a;
  border-radius: 10px;
  color: #e4e4e7;
  font-size: 0.9rem;
  font-family: inherit;
  outline: none;
  transition: border-color 0.2s, box-shadow 0.2s;
}

.combobox-input:focus {
  border-color: #3b82f6;
  box-shadow: 0 0 0 3px rgba(59, 130, 246, 0.15);
}

.combobox-input::placeholder {
  color: #52525b;
}

.combobox-clear {
  position: absolute;
  right: 0.6rem;
  display: flex;
  align-items: center;
  justify-content: center;
  width: 28px;
  height: 28px;
  background: transparent;
  border: none;
  color: #52525b;
  cursor: pointer;
  border-radius: 6px;
  transition: all 0.15s;
}

.combobox-clear:hover {
  background: #1e1e22;
  color: #a1a1aa;
}

.combobox-clear:focus-visible {
  outline: 2px solid #3b82f6;
  outline-offset: 2px;
}

.combobox-clear[hidden] {
  display: none;
}

/* Listbox */
.combobox-listbox {
  position: absolute;
  top: calc(100% + 4px);
  left: 0;
  right: 0;
  background: #111113;
  border: 1px solid #27272a;
  border-radius: 10px;
  list-style: none;
  max-height: 280px;
  overflow-y: auto;
  z-index: 100;
  box-shadow: 0 12px 40px rgba(0, 0, 0, 0.4);
  padding: 4px;
  animation: dropIn 0.15s ease-out;
}

.combobox-listbox[hidden] {
  display: none;
}

.combobox-option {
  padding: 0.55rem 0.85rem;
  font-size: 0.875rem;
  color: #d4d4d8;
  border-radius: 6px;
  cursor: pointer;
  display: flex;
  align-items: center;
  gap: 0.6rem;
  transition: background 0.1s;
}

.combobox-option:hover {
  background: #1e1e22;
}

.combobox-option--active {
  background: rgba(59, 130, 246, 0.12);
  color: #60a5fa;
}

.combobox-option[aria-selected="true"] {
  color: #3b82f6;
}

.combobox-option[aria-selected="true"]::after {
  content: "";
  margin-left: auto;
  width: 16px;
  height: 16px;
  background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='16' height='16' viewBox='0 0 24 24' fill='none' stroke='%233b82f6' stroke-width='2.5' stroke-linecap='round' stroke-linejoin='round'%3E%3Cpolyline points='20 6 9 17 4 12'/%3E%3C/svg%3E");
  background-size: contain;
  background-repeat: no-repeat;
}

.combobox-option-flag {
  font-size: 1.1rem;
  line-height: 1;
}

.combobox-no-results {
  padding: 1rem;
  font-size: 0.85rem;
  color: #52525b;
  text-align: center;
}

/* Status */
.combobox-status {
  font-size: 0.78rem;
  color: #52525b;
  margin-top: 0.35rem;
  min-height: 1.25rem;
}

/* Selected display */
.selected-display {
  margin-top: 1.25rem;
  padding-top: 1rem;
  border-top: 1px solid #1e1e22;
  display: flex;
  align-items: center;
  gap: 0.5rem;
}

.selected-label {
  font-size: 0.8rem;
  color: #71717a;
}

.selected-value {
  font-size: 0.9rem;
  font-weight: 500;
  color: #fafafa;
}

/* Info Panel */
.info-panel {
  margin-top: 2rem;
  background: #111113;
  border: 1px solid #27272a;
  border-radius: 12px;
  padding: 1.5rem;
}

.info-title {
  font-size: 1rem;
  font-weight: 600;
  color: #fafafa;
  margin-bottom: 0.75rem;
}

.info-subtitle {
  font-size: 0.9rem;
  font-weight: 600;
  color: #fafafa;
  margin-top: 1.25rem;
  margin-bottom: 0.5rem;
}

.info-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 0.5rem;
}

.info-item {
  display: flex;
  flex-direction: column;
  gap: 0.15rem;
  font-size: 0.8rem;
  color: #71717a;
}

.info-item code {
  background: #1e1e22;
  padding: 0.12rem 0.4rem;
  border-radius: 4px;
  font-size: 0.75rem;
  color: #60a5fa;
  font-family: "SF Mono", "Fira Code", monospace;
  width: fit-content;
}

.kbd-grid {
  display: flex;
  flex-direction: column;
  gap: 0.35rem;
}

.kbd-item {
  font-size: 0.8rem;
  color: #a1a1aa;
}

kbd {
  display: inline-block;
  padding: 0.08rem 0.4rem;
  background: #1e1e22;
  border: 1px solid #3f3f46;
  border-radius: 4px;
  font-size: 0.73rem;
  font-family: "SF Mono", "Fira Code", monospace;
  color: #d4d4d8;
  margin-right: 0.25rem;
}

/* Scrollbar */
.combobox-listbox::-webkit-scrollbar {
  width: 4px;
}

.combobox-listbox::-webkit-scrollbar-track {
  background: transparent;
}

.combobox-listbox::-webkit-scrollbar-thumb {
  background: #27272a;
  border-radius: 4px;
}

@keyframes dropIn {
  from {
    opacity: 0;
    transform: translateY(-4px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

(() => {
  const countries = [
    { name: "Argentina", flag: "\uD83C\uDDE6\uD83C\uDDF7" },
    { name: "Australia", flag: "\uD83C\uDDE6\uD83C\uDDFA" },
    { name: "Brazil", flag: "\uD83C\uDDE7\uD83C\uDDF7" },
    { name: "Canada", flag: "\uD83C\uDDE8\uD83C\uDDE6" },
    { name: "China", flag: "\uD83C\uDDE8\uD83C\uDDF3" },
    { name: "Denmark", flag: "\uD83C\uDDE9\uD83C\uDDF0" },
    { name: "Egypt", flag: "\uD83C\uDDEA\uD83C\uDDEC" },
    { name: "France", flag: "\uD83C\uDDEB\uD83C\uDDF7" },
    { name: "Germany", flag: "\uD83C\uDDE9\uD83C\uDDEA" },
    { name: "India", flag: "\uD83C\uDDEE\uD83C\uDDF3" },
    { name: "Italy", flag: "\uD83C\uDDEE\uD83C\uDDF9" },
    { name: "Japan", flag: "\uD83C\uDDEF\uD83C\uDDF5" },
    { name: "Kenya", flag: "\uD83C\uDDF0\uD83C\uDDEA" },
    { name: "Mexico", flag: "\uD83C\uDDF2\uD83C\uDDFD" },
    { name: "Netherlands", flag: "\uD83C\uDDF3\uD83C\uDDF1" },
    { name: "Norway", flag: "\uD83C\uDDF3\uD83C\uDDF4" },
    { name: "Portugal", flag: "\uD83C\uDDF5\uD83C\uDDF9" },
    { name: "South Korea", flag: "\uD83C\uDDF0\uD83C\uDDF7" },
    { name: "Spain", flag: "\uD83C\uDDEA\uD83C\uDDF8" },
    { name: "Sweden", flag: "\uD83C\uDDF8\uD83C\uDDEA" },
    { name: "United Kingdom", flag: "\uD83C\uDDEC\uD83C\uDDE7" },
    { name: "United States", flag: "\uD83C\uDDFA\uD83C\uDDF8" },
  ];

  const input = document.getElementById("country-input");
  const listbox = document.getElementById("country-listbox");
  const combobox = document.querySelector('[role="combobox"]');
  const clearBtn = document.getElementById("clear-input");
  const statusEl = document.getElementById("combobox-status");
  const selectedValue = document.getElementById("selected-value");

  let activeIndex = -1;
  let filteredCountries = [...countries];
  let isOpen = false;

  function renderOptions(filter = "") {
    const query = filter.toLowerCase().trim();
    filteredCountries = query
      ? countries.filter((c) => c.name.toLowerCase().includes(query))
      : [...countries];

    listbox.innerHTML = "";
    activeIndex = -1;

    if (filteredCountries.length === 0) {
      listbox.innerHTML = '<li class="combobox-no-results">No countries found</li>';
      updateStatus("No results");
      return;
    }

    filteredCountries.forEach((country, i) => {
      const li = document.createElement("li");
      li.id = `option-${i}`;
      li.className = "combobox-option";
      li.setAttribute("role", "option");
      li.setAttribute("aria-selected", "false");
      li.innerHTML = `<span class="combobox-option-flag" aria-hidden="true">${country.flag}</span>${country.name}`;

      li.addEventListener("click", () => selectOption(i));
      li.addEventListener("mouseenter", () => {
        setActiveOption(i, false);
      });

      listbox.appendChild(li);
    });

    const count = filteredCountries.length;
    updateStatus(
      count === 1
        ? "1 result available"
        : `${count} results available. Use Up and Down arrows to navigate.`
    );
  }

  function updateStatus(text) {
    statusEl.textContent = text;
  }

  function openListbox() {
    if (isOpen) return;
    isOpen = true;
    listbox.hidden = false;
    combobox.setAttribute("aria-expanded", "true");
    renderOptions(input.value);
  }

  function closeListbox() {
    if (!isOpen) return;
    isOpen = false;
    listbox.hidden = true;
    combobox.setAttribute("aria-expanded", "false");
    input.setAttribute("aria-activedescendant", "");
    activeIndex = -1;
    updateStatus("");
  }

  function setActiveOption(index, scroll = true) {
    // Remove active from previous
    const options = listbox.querySelectorAll('[role="option"]');
    options.forEach((opt) => opt.classList.remove("combobox-option--active"));

    if (index < 0 || index >= filteredCountries.length) {
      activeIndex = -1;
      input.setAttribute("aria-activedescendant", "");
      return;
    }

    activeIndex = index;
    const activeEl = options[index];
    activeEl.classList.add("combobox-option--active");
    input.setAttribute("aria-activedescendant", activeEl.id);

    if (scroll) {
      activeEl.scrollIntoView({ block: "nearest" });
    }
  }

  function selectOption(index) {
    const country = filteredCountries[index];
    if (!country) return;

    input.value = country.name;
    selectedValue.textContent = `${country.flag} ${country.name}`;
    clearBtn.hidden = false;

    // Mark as selected
    const options = listbox.querySelectorAll('[role="option"]');
    options.forEach((opt) => opt.setAttribute("aria-selected", "false"));
    if (options[index]) {
      options[index].setAttribute("aria-selected", "true");
    }

    closeListbox();
    updateStatus(`${country.name} selected`);
  }

  // Input events
  input.addEventListener("input", () => {
    clearBtn.hidden = !input.value;
    if (!isOpen) openListbox();
    renderOptions(input.value);
  });

  input.addEventListener("focus", () => {
    openListbox();
  });

  input.addEventListener("keydown", (e) => {
    const optionCount = filteredCountries.length;

    switch (e.key) {
      case "ArrowDown":
        e.preventDefault();
        if (!isOpen) {
          openListbox();
        } else {
          setActiveOption(activeIndex < optionCount - 1 ? activeIndex + 1 : 0);
        }
        break;

      case "ArrowUp":
        e.preventDefault();
        if (!isOpen) {
          openListbox();
        } else {
          setActiveOption(activeIndex > 0 ? activeIndex - 1 : optionCount - 1);
        }
        break;

      case "Home":
        if (isOpen && optionCount > 0) {
          e.preventDefault();
          setActiveOption(0);
        }
        break;

      case "End":
        if (isOpen && optionCount > 0) {
          e.preventDefault();
          setActiveOption(optionCount - 1);
        }
        break;

      case "Enter":
        e.preventDefault();
        if (isOpen && activeIndex >= 0) {
          selectOption(activeIndex);
        }
        break;

      case "Escape":
        if (isOpen) {
          e.preventDefault();
          closeListbox();
        }
        break;
    }
  });

  // Clear button
  clearBtn.addEventListener("click", () => {
    input.value = "";
    clearBtn.hidden = true;
    selectedValue.textContent = "None";
    input.focus();
    renderOptions("");
  });

  // Close on outside click
  document.addEventListener("click", (e) => {
    if (!e.target.closest(".combobox-wrapper")) {
      closeListbox();
    }
  });

  // Initialize
  renderOptions("");
})();

<!doctype html>
<html lang="en">
<head>
  <meta charset="UTF-8" />
  <meta name="viewport" content="width=device-width, initial-scale=1.0" />
  <title>ARIA Combobox</title>
  <link rel="stylesheet" href="style.css" />
</head>
<body>
  <div class="demo">
    <h1 class="demo-title">ARIA Combobox</h1>
    <p class="demo-sub">Accessible autocomplete implementing ARIA 1.2 combobox pattern with keyboard navigation.</p>

    <div class="combobox-section">
      <div class="combobox-container">
        <label class="combobox-label" id="country-label" for="country-input">Select a country</label>
        <div class="combobox-wrapper">
          <div class="combobox-input-wrap"
               role="combobox"
               aria-expanded="false"
               aria-haspopup="listbox"
               aria-owns="country-listbox">
            <svg class="combobox-search-icon" aria-hidden="true" xmlns="http://www.w3.org/2000/svg" width="16" height="16" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round"><circle cx="11" cy="11" r="8"/><line x1="21" y1="21" x2="16.65" y2="16.65"/></svg>
            <input type="text"
                   id="country-input"
                   class="combobox-input"
                   aria-autocomplete="list"
                   aria-controls="country-listbox"
                   aria-activedescendant=""
                   aria-labelledby="country-label"
                   placeholder="Type to search countries..."
                   autocomplete="off" />
            <button class="combobox-clear" id="clear-input" aria-label="Clear selection" hidden>
              <svg xmlns="http://www.w3.org/2000/svg" width="14" height="14" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round"><line x1="18" y1="6" x2="6" y2="18"/><line x1="6" y1="6" x2="18" y2="18"/></svg>
            </button>
          </div>
          <ul id="country-listbox"
              class="combobox-listbox"
              role="listbox"
              aria-labelledby="country-label"
              hidden>
            <!-- Options populated by JS -->
          </ul>
        </div>
        <div class="combobox-status" role="status" aria-live="polite" id="combobox-status"></div>
      </div>

      <div class="selected-display">
        <span class="selected-label">Selected:</span>
        <span class="selected-value" id="selected-value">None</span>
      </div>
    </div>

    <!-- Info Panel -->
    <div class="info-panel">
      <h3 class="info-title">ARIA Attributes</h3>
      <div class="info-grid">
        <div class="info-item">
          <code>role="combobox"</code>
          <span>Container wrapping the input</span>
        </div>
        <div class="info-item">
          <code>role="listbox"</code>
          <span>The dropdown options list</span>
        </div>
        <div class="info-item">
          <code>role="option"</code>
          <span>Each selectable item</span>
        </div>
        <div class="info-item">
          <code>aria-expanded</code>
          <span>Whether the listbox is open</span>
        </div>
        <div class="info-item">
          <code>aria-activedescendant</code>
          <span>ID of the focused option</span>
        </div>
        <div class="info-item">
          <code>aria-autocomplete="list"</code>
          <span>Filtering suggestions are shown</span>
        </div>
      </div>
      <h4 class="info-subtitle">Keyboard Controls</h4>
      <div class="kbd-grid">
        <span class="kbd-item"><kbd>Down</kbd> Open listbox / next option</span>
        <span class="kbd-item"><kbd>Up</kbd> Previous option</span>
        <span class="kbd-item"><kbd>Enter</kbd> Select highlighted option</span>
        <span class="kbd-item"><kbd>Escape</kbd> Close listbox</span>
        <span class="kbd-item"><kbd>Home</kbd> First option</span>
        <span class="kbd-item"><kbd>End</kbd> Last option</span>
      </div>
    </div>
  </div>

  <script src="script.js"></script>
</body>
</html>

An autocomplete combobox implementing the ARIA 1.2 combobox pattern with type-to-filter, keyboard navigation (Up/Down/Enter/Escape), and aria-activedescendant management. Result counts are announced via a live region for screen reader users.