/* Use this to cause a function to fire no more than once every 'ms' milliseconds.
   For example, an expensive mousemove handler:
   
   $('body').mouseover(ratelimit(function(ev) {
      // ...
   }, 250));
*/

function ratelimit(fn, ms) {
    var last = (new Date()).getTime();
    return (function() {
        var now = (new Date()).getTime();
        if (now - last > ms) {
            last = now;
            fn.apply(null, arguments);
        }
    });
}