Naughty Praying Mantis


    2.0.2 • Public • Published

    Browser Keymap

    A small library for doing sane key binding in the browser. It defines two things:

    A string notation for key events

    browserkeymap keys are represented by strings like "Shift-Space", "Ctrl-Alt-Delete", or "'x'". The rules are:

    • keypress events are represented as the character that was typed between single quotes. They do not support modifiers because browsers do not attach modifier information to keypress events.

    • keydown events are represented as zero or more modifiers (Shift-, Cmd-, Alt-, Ctrl-) followed by a key name.

    • A key name is a capital letter for a letter key, a digit for a number key, F plus a number for a function key, the symbol typed by the key when shift isn't held down (one of [\]`'*,-./;=), or one of the names Alt, Backspace, CapsLock, Ctrl, Delete, Down, End, Enter, Esc, Home, Insert, Left, Mod, PageDown, PageUp, Pause, PrintScrn, Right, Shift, Space, Tab, or Up.

    You can get a key name from an event by calling Keymap.keyName(event).

    You can normalize a key name string (fixing the order of the modifiers, and replacing alternative modifier names with their standard name) by calling Keymap.normalizeKeyName(string). This function maps the modifier Mod- to Cmd- on Mac platforms and to Ctrl- on non-Mac platforms. It also accepts a- for Alt-, c- or Control- for Ctrl-, m- or Meta- for Cmd-, and s- for Shift-.

    You can use Keymap.isModifierKey(string) to find out whether the given key name refers to a modifier key.

    An object type for keymaps

    The Keymap constructor itself, which is the thing the library exports, can be used to build keymaps.

    var myMap = new Keymap({
      "Ctrl-Q": handleQuit,
      "Shift-Space": autocomplete

    A keymap associates keys with values. You can call its lookup method to look up a key:

    myMap.lookup("Ctrl-Q") // → handleQuit
    myMap.lookup("Alt-F4") // → undefined

    You can create a new map from an existing map with its update method:

    var newMap = myMap.update({
      "Alt-F4": handleQuit,
      "Ctrl-Q": null

    That will create a new map, starting with the bindings in myMap, adding a binding for Alt-F4, and removing the binding for Ctrl-Q.

    Multi-stroke keys are supported by providing space-separated names to a keymap. When a prefix of a multi-stroke key is looked up, the lookup method will return Keymap.unfinished. The handler should then buffer the key name, and on the next key event (possibly with a timeout to clear buffered keys), try again by prefixing the new key event's name with the buffered key(s).


    This module is released under an MIT license.


    npm i browserkeymap

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    • marijn