Passing a float (instead of an integer) drives node's setTimeout nuts.

setTimeoutProblem.js

// sets kCount timeouts of no more than 5 ms using floats and using integers
// and logs the times at which they are actually triggered.

var t0;
var log= [];
var kCount= 20;
function go () {
  var i= kCount;
  var cb= f('FLOAT');
  while (i--) setTimeout(cb, Math.random()*5);
  
  var i= kCount;
  var cb= f('INT');
  while (i--) setTimeout(cb, Math.floor(Math.random()*5));
  
  t0= Date.now();
}

function f (t) {
  return function () {
    log.push([Date.now()-t0, t]);
  };
}

function printLog () {
  var txt= '';
  log.forEach(cat);
  process.stdout.write(new Buffer(txt));
  process.stdout.flush();
  
  function cat (t, i) {
    txt+= '[' + i + '] ' + t[0] + ' ms, '+ t[1]+ '\n';
  }
}

go();
process.on('exit', printLog);