@github/hotkey

Hotkey Behavior

<button data-hotkey="Shift+?">Show help dialog</button>

Trigger an action on a target element when the hotkey (key or sequence of keys) is pressed on the keyboard. This triggers a focus event on form fields, or a click event on other elements.

The hotkey can be scoped to a form field:

<button data-hotkey-scope="text-area" data-hotkey="Meta+d" onclick="alert('clicked')">
  press meta+d in text area to click this button
</button>

<textarea id="text-area">text area</textarea>

By default, hotkeys are extracted from a target element's data-hotkey attribute, but this can be overridden by passing the hotkey to the registering function (install) as a parameter.

How is this used on GitHub?

All shortcuts (for example g i, ., Meta+k) within GitHub use hotkey to declare shortcuts in server side templates. This is used on almost every page on GitHub.

Installation

$ npm install @github/hotkey

Usage

HTML

<!-- Single character hotkey: triggers when "j" is pressed-->
<a href="/page/2" data-hotkey="j">Next</a>
<!-- Multiple hotkey aliases: triggers on both "s" and "/" -->
<a href="/search" data-hotkey="s,/">Search</a>
<!-- Key-sequence hotkey: triggers when "g" is pressed followed by "c"-->
<a href="/rails/rails" data-hotkey="g c">Code</a>
<!-- Hotkey with modifiers: triggers when "Control", "Alt", and "h" are pressed at the same time -->
<a href="/help" data-hotkey="Control+Alt+h">Help</a>
<!-- Special "Mod" modifier localizes to "Meta" on mac, "Control" on Windows or Linux-->
<a href="/settings" data-hotkey="Mod+s">Search</a>

See the list of KeyboardEvent key values for a list of supported key values.

JS

import {install} from '@github/hotkey'

// Install all the hotkeys on the page
for (const el of document.querySelectorAll('[data-hotkey]')) {
  install(el)
}

Alternatively, the hotkey(s) can be passed to the install function as a parameter e.g.:

for (const el of document.querySelectorAll('[data-shortcut]')) {
  install(el, el.dataset.shortcut)
}

To unregister a hotkey from an element, use uninstall:

import {uninstall} from '@github/hotkey'

for (const el of document.querySelectorAll('[data-hotkey]')) {
  uninstall(el)
}

By default form elements (such as input,textarea,select) or elements with contenteditable will call focus() when the hotkey is triggered. All other elements trigger a click(). All elements, regardless of type, will emit a cancellable hotkey-fire event, so you can customize the behaviour, if you so choose:

for (const el of document.querySelectorAll('[data-shortcut]')) {
  install(el, el.dataset.shortcut)

  if (el.matches('.frobber')) {
    el.addEventListener('hotkey-fire', event => {
      // ensure the default `focus()`/`click()` is prevented:
      event.preventDefault()

      // Use a custom behaviour instead
      frobulateFrobber(event.target)
    })
  }
}

Hotkey string format

1. Hotkey matches against the event.key, and uses standard W3C key names for keys and modifiers as documented in UI Events KeyboardEvent key Values.
2. At minimum a hotkey string must specify one bare key.
3. Multiple hotkeys (aliases) are separated by a ,. For example the hotkey a,b would activate if the user typed a or b.
4. Multiple keys separated by a blank space represent a key sequence. For example the hotkey g n would activate when a user types the g key followed by the n key.
5. Modifier key combos are separated with a + and are prepended to a key in a consistent order as follows: "Control+Alt+Meta+Shift+KEY".
6. "Mod" is a special modifier that localizes to Meta on MacOS/iOS, and Control on Windows/Linux.
   1. "Mod+" can appear in any order in a hotkey string. For example: "Mod+Alt+Shift+KEY"
   2. Neither the Control or Meta modifiers should appear in a hotkey string with Mod.
7. "Plus" and "Space" are special key names to represent the + and keys respectively, because these symbols cannot be represented in the normal hotkey string syntax.
8. You can use the comma key , as a hotkey, e.g. a,, would activate if the user typed a or ,. Control+,,x would activate for Control+, or x.
9. "Shift" should be included if it would be held and the key is uppercase: ie, Shift+A not A
   1. MacOS outputs lowercase key names when Meta+Shift is held (ie, Meta+Shift+a). In an attempt to normalize this, hotkey will automatically map these key names to uppercase, so the uppercase keys should still be used (ie, "Meta+Shift+A" or "Mod+Shift+A"). However, this normalization only works on US keyboard layouts.

Example

The following hotkey would match if the user typed the key sequence a and then b, OR if the user held down the Control, Alt and / keys at the same time.

'a b,Control+Alt+/'

🔬 Hotkey Mapper is a tool to help you determine the correct hotkey string for your key combination: https://github.github.io/hotkey/hotkey_mapper.html

Key-sequence considerations

Two-key-sequences such as g c and g i are stored under the 'g' key in a nested object with 'c' and 'i' keys.

mappings =
  'c'     : <a href="/rails/rails/issues/new" data-hotkey="c">New Issue</a>
  'g'     :
    'c'   : <a href="/rails/rails" data-hotkey="g c">Code</a>
    'i'   : <a href="/rails/rails/issues" data-hotkey="g i">Issues</a>

In this example, both g c and c could be available as hotkeys on the same page, but g c and g can't coexist. If the user presses g, the c hotkey will be unavailable for 1500 ms while we wait for either g c or g i.

Accessibility considerations

Character Key Shortcuts

Please note that adding this functionality to your site can be a drawback for certain users. Providing a way in your system to disable hotkeys or remap them makes sure that those users can still use your site (given that it's accessible to those users).

See "Understanding Success Criterion 2.1.4: Character Key Shortcuts" for further reading on this topic.

Interactive Elements

Wherever possible, hotkeys should be add to interactive and focusable elements. If a static element must be used, please follow the guideline in "Adding keyboard-accessible actions to static HTML elements".

Development

npm install
npm test

License

Distributed under the MIT license. See LICENSE for details.