Modes for flashing the window icon in the taskbar:

• "auto" - the icon will flash only if the window isn't on focus and will stop flashing when the window is activated;
• "force" - the icon will flash even if the window is on focus, but still turns off when the window is activated;
• "forceAndKeep" - the icon will flash until the flash() method is called with false as an argument;

• "auto"
• "force"
• "forceAndKeep"