The HTML5 specifications states that setTimeout can be run without the additional "timeout" argument which is supposed to say after how many milliseconds will the function "handler" be scheduled.

handle = window . setTimeout( handler [, timeout [, arguments ] ] )
   Schedules a timeout to run handler after timeout milliseconds. Any arguments are passed straight through to the handler.

However, I failed to find anywhere which explains what happens when no "timeout" time period is set.

An example usage is, the animation implementation int the Raphael library.

animationElements[length] && win.setTimeout(animation);