A JavaScript micro-library for cross-browser keyboard event handling.

micromousetrap.js

// This is an attempt to paper over the keycode differences between
// Gecko and WebKit (e.g. Iceweasel or Firefox and Chrome or
// Chromium), somewhat following the model of Mousetrap:
// <https://github.com/ccampbell/mousetrap>.
// The mapping tables herein are far from comprehensive, implementing
// more or less only what I need for this calculator.
function decodeKeyEvent(event) {
  return decodeKeyEventProperties(event.key, event.keyCode, event.shiftKey);
}

var decodeKeyEventProperties = (
  function() {
    function decodeKeyEventProperties(key, keyCode, shift) {
      if (key) return key;
      var c =
        _keyCodeMap[keyCode] || String.fromCharCode(keyCode).toLowerCase();
      return (shift ? shifted(c) : c);
    }
    // Keys which, in WebKit browsers (and I guess IE?), have the
    // wrong codes, or which have symbolic names in DOM 3.
    // Too bad ← maps to % and → maps to ', no?  ' in WebKit is 222.
    // Fortunately Firefox gives us DOM 3 `key`, so this won’t break
    // Firefox.
    var _keyCodeMap = {187: '=', 189: "-", 191: "/",
                       37: "Left", 39: "Right",
                       222: "'", 8: "Backspace"};

    var unshiftedKeys = "`1234567890-=,"
      , reshiftedKeys = "~!@#$%^&*[]_+<"
    ;
    var shiftMap = {};
    for (var i = 0; i < unshiftedKeys.length; i++) {
      shiftMap[unshiftedKeys.charAt(i)] = reshiftedKeys.charAt(i);
    }

    return decodeKeyEventProperties;

    function shifted(c) {
      return shiftMap[c] || c.toUpperCase();
    }
  })();