Have you looked at Breakout/examples/getting_started/hello_world.html. All this uses is an LED and button. It will still work even if you don’t wire up the button.
To turn an LED on or off you can use the on() and off() methods of the LED. For example, you can change line 63 of the hello_world.html example to:
and then after a delay (using setTimeout) turn it off using:
If you want to blink or fade an LED at a regular interval, then it is best to use the blink() method and pass a waveform as illustrated in the hello_world example.