code: function checkKeyCodes (
    eventKeyCode,
    key,
    builtInKeyCode,
    eventKeyName,
    builtInKeyName
  ) {
    const mappedKeyCode = config.keyCodes[key] || builtInKeyCode;
    if (builtInKeyName && eventKeyName && !config.keyCodes[key]) {
      return isKeyNotMatch(builtInKeyName, eventKeyName)
    } else if (mappedKeyCode) {
      return isKeyNotMatch(mappedKeyCode, eventKeyCode)
    } else if (eventKeyName) {
      return hyphenate(eventKeyName) !== key
    }
  }
docs: Runtime helper for checking keyCodes from config.
  exposed as Vue.prototype._k
  passing in eventKeyName as last argument separately for backwards compat