function mergeIf(baseTable, select, table) {
    if (browser_os === select || browser === select || os === select) {
      Object.keys(table).forEach(function(keyCode) {
        baseTable[keyCode] = table[keyCode];
      });
    }
  }
Polyfill for the additional KeyboardEvent properties defined in the D3E and
D4E draft specifications, by @inexorabletash.

See: https://github.com/inexorabletash/polyfill