Timers for Animation

• This is a side trip.
  • And fairly shallow at that.
• Most operating systems support the idea of timers.
  • After an interval has elapsed a function is called.
• This is then easily extended to programs.
• Javascript support two basic tools for this
  • A timer, or one shot call. setTimeout
  • An interval or a continuous call. setInterval
• In either case, they take
  • A function to be called
  • An optional time, in milliseconds to wait until the function is called
    • If this is 0 (or not given), the function is called immediately
    • Or, better yet, at the bottom of the next event loop.
    • The delay may be longer than the given delay
  • A set of optional arguments.
• Either case, they return a timer id.
• This can be used to cancel the timer
  • clearTimeout
  • clearInterval.
• You really only want one timeout/interval running for your main animation.
  • If you set multiple timers, with the same callback function, it will try to do it.
  • Which will nullify your delay.
  • Think reseeding the random number generator , but worse
• And you really want that callback function to finish in less than the delay given.