Add support for Home and End keys

The [WAI ARIA Practices 1.1][listbox-keyboard] outlines optional support
for [`Home` and `End` keys][keys] to jump to the top and bottom of the
listbox, respectively.

[listbox-keyboard]: https://www.w3.org/WAI/ARIA/apg/patterns/combobox/#listbox-popup-keyboard-interaction
[keys]: https://www.w3.org/TR/uievents-key/#keys-navigation

Configure: Home and End navigation
---

By default, continue to ignore `Home` and `End` navigation keys.

When `optionalNavigationKeys: ["Home", "End"]` is passed as a
configuration object, treat them as valid navigation keys.

Author: seanpdoyle

Diff for: README.md

@@ -94,9 +94,11 @@ These settings are available:
   > **Warning** Screen readers will not announce that the first item is the default. This should be announced explicitly with the use of `aria-live` status text.
 - `scrollIntoViewOptions?: boolean | ScrollIntoViewOptions = undefined` - When
   controlling the element marked `[aria-selected="true"]` with keyboard navigation, the selected element will be scrolled into the viewport by a call to [Element.scrollIntoView][]. Configure this value to control the scrolling behavior (either with a `boolean` or a [ScrollIntoViewOptions][] object.
+- `optionalNavigationKeys?: Array<'Home' | 'End'>  = []` - When navigating the list, enable additional [Navigation Keys][], like <kbd>Home</kbd> to skip to the top of the list and <kbd>End</kbd> to skip to the bottom.
 
 [Element.scrollIntoView]: https://developer.mozilla.org/en-US/docs/Web/API/Element/scrollIntoView
 [ScrollIntoViewOptions]: https://developer.mozilla.org/en-US/docs/Web/API/Element/scrollIntoView#sect1
+[Navigation Keys]: https://www.w3.org/TR/uievents-key/#keys-home
 
 
 ## Development

Diff for: src/index.ts

@@ -1,7 +1,10 @@
+type OptionalNavigationKeys = 'Home' | 'End'
+
 export type ComboboxSettings = {
   tabInsertsSuggestions?: boolean
   defaultFirstOption?: boolean
   scrollIntoViewOptions?: boolean | ScrollIntoViewOptions
+  optionalNavigationKeys?: OptionalNavigationKeys[]
 }
 
 export default class Combobox {
@@ -15,17 +18,19 @@ export default class Combobox {
   tabInsertsSuggestions: boolean
   defaultFirstOption: boolean
   scrollIntoViewOptions?: boolean | ScrollIntoViewOptions
+  optionalNavigationKeys: OptionalNavigationKeys[]
 
   constructor(
     input: HTMLTextAreaElement | HTMLInputElement,
     list: HTMLElement,
-    {tabInsertsSuggestions, defaultFirstOption, scrollIntoViewOptions}: ComboboxSettings = {},
+    {tabInsertsSuggestions, defaultFirstOption, scrollIntoViewOptions, optionalNavigationKeys}: ComboboxSettings = {},
   ) {
     this.input = input
     this.list = list
     this.tabInsertsSuggestions = tabInsertsSuggestions ?? true
     this.defaultFirstOption = defaultFirstOption ?? false
     this.scrollIntoViewOptions = scrollIntoViewOptions
+    this.optionalNavigationKeys = optionalNavigationKeys ?? []
 
     this.isComposing = false
 
@@ -154,6 +159,20 @@ function keyboardBindings(event: KeyboardEvent, combobox: Combobox) {
       combobox.navigate(-1)
       event.preventDefault()
       break
+    case 'Home':
+      if (combobox.optionalNavigationKeys.includes('Home')) {
+        combobox.clearSelection()
+        combobox.navigate(1)
+        event.preventDefault()
+      }
+      break
+    case 'End':
+      if (combobox.optionalNavigationKeys.includes('End')) {
+        combobox.clearSelection()
+        combobox.navigate(-1)
+        event.preventDefault()
+      }
+      break
     case 'n':
       if (combobox.ctrlBindings && event.ctrlKey) {
         combobox.navigate(1)

Diff for: test/test.js

@@ -311,4 +311,74 @@ describe('combobox-nav', function () {
       })
     })
   })
+
+  describe('with Home key navigation enabled', () => {
+    let input
+    let list
+    let options
+    let combobox
+    beforeEach(() => {
+      document.body.innerHTML = `
+        <input type="text">
+        <ul role="listbox" id="list-id">
+          <li id="baymax" role="option">Baymax</li>
+          <li><del>BB-8</del></li>
+          <li id="hubot" role="option">Hubot</li>
+          <li id="r2-d2" role="option">R2-D2</li>
+          <li id="johnny-5" hidden role="option">Johnny 5</li>
+          <li id="wall-e" role="option" aria-disabled="true">Wall-E</li>
+          <li><a href="#link" role="option" id="link">Link</a></li>
+        </ul>
+      `
+      input = document.querySelector('input')
+      list = document.querySelector('ul')
+      options = document.querySelectorAll('[role=option]')
+      combobox = new Combobox(input, list, {optionalNavigationKeys: ['Home']})
+      combobox.start()
+    })
+
+    it('updates attributes on keyboard events', () => {
+      press(input, 'ArrowDown')
+      press(input, 'ArrowDown')
+
+      assert.equal(options[1].getAttribute('aria-selected'), 'true')
+      assert.equal(input.getAttribute('aria-activedescendant'), 'hubot')
+
+      press(input, 'Home')
+      assert.equal(options[0].getAttribute('aria-selected'), 'true')
+      assert.equal(input.getAttribute('aria-activedescendant'), 'baymax')
+    })
+  })
+
+  describe('with End key navigation enabled', () => {
+    let input
+    let list
+    let options
+    let combobox
+    beforeEach(() => {
+      document.body.innerHTML = `
+        <input type="text">
+        <ul role="listbox" id="list-id">
+          <li id="baymax" role="option">Baymax</li>
+          <li><del>BB-8</del></li>
+          <li id="hubot" role="option">Hubot</li>
+          <li id="r2-d2" role="option">R2-D2</li>
+          <li id="johnny-5" hidden role="option">Johnny 5</li>
+          <li id="wall-e" role="option" aria-disabled="true">Wall-E</li>
+          <li><a href="#link" role="option" id="link">Link</a></li>
+        </ul>
+      `
+      input = document.querySelector('input')
+      list = document.querySelector('ul')
+      options = document.querySelectorAll('[role=option]')
+      combobox = new Combobox(input, list, {optionalNavigationKeys: ['End']})
+      combobox.start()
+    })
+
+    it('updates attributes on keyboard events', () => {
+      press(input, 'End')
+      assert.equal(options[5].getAttribute('aria-selected'), 'true')
+      assert.equal(input.getAttribute('aria-activedescendant'), 'link')
+    })
+  })
 })