code: function key_identifier_sane(keyCode, keyIdentifier) {
  
          // Missing identifier is not sane
          if (!keyIdentifier)
              return false;
  
          // Assume non-Unicode keyIdentifier values are sane
          var unicodePrefixLocation = keyIdentifier.indexOf("U+");
          if (unicodePrefixLocation === -1)
              return true;
  
          // If the Unicode codepoint isn't identical to the keyCode,
          // then the identifier is likely correct
          var codepoint = parseInt(keyIdentifier.substring(unicodePrefixLocation+2), 16);
          if (keyCode !== codepoint)
              return true;
  
          // The keyCodes for A-Z and 0-9 are actually identical to their
          // Unicode codepoints
          if ((keyCode >= 65 && keyCode <= 90) || (keyCode >= 48 && keyCode <= 57))
              return true;
  
          // The keyIdentifier does NOT appear sane
          return false;
  
      }
docs: Heuristically detects if the legacy keyIdentifier property of
  a keydown/keyup event looks incorrectly derived. Chrome, and
  presumably others, will produce the keyIdentifier by assuming
  the keyCode is the Unicode codepoint for that key. This is not
  correct in all cases.
  
  @private
  @param {Number} keyCode
  The keyCode from a browser keydown/keyup event.
  
  @param {String} keyIdentifier
  The legacy keyIdentifier from a browser keydown/keyup event.
  
  @returns {Boolean}
  true if the keyIdentifier looks sane, false if the keyIdentifier
  appears incorrectly derived or is missing entirely.