quick function to help with staggered rollout of features or updates

staggered_rollout.js

// example staggering rollout over 24 hours, timeToStart is date timestamp ms.  
// if(staggeredRollout(timeToStart,timeToStart+(1000*60*60*24), 24, customerId)){ someNewThing()  }  

function staggeredRollout(startAt, endAt, stages, input, now){
  now = now || (new Date()).getTime();
  if( now < startAt ) return false;
  if( now >= endAt ) return true;
  var hash = strToHashCode(input);
  var period = (endAt - startAt) / stages;
  var currentStage = Math.floor( (now - startAt) / period );  
  var inputStage = (hash % stages); 
  var result = inputStage <= currentStage;
  console.log("" + currentStage +' : '+  inputStage +' => '+ result)
  return result; 
}

function strToHashCode(str) {
  var hash = 0, i, chr;
  if (str.length === 0) return hash;
  for (i = 0; i < str.length; i++) {
    chr   = str.charCodeAt(i);
    hash  = ((hash << 5) - hash) + chr;
    hash |= 0;
  }
  return hash
}

function test(){
  

  var now = (new Date()).getTime();
  var startAt = now;
  var endAt = now + (10*1000);
  var stages = 5; 
  console.log("test"); 
  staggeredRollout(startAt, endAt, stages, "foo", now-1);
  staggeredRollout(startAt, endAt, stages, "foo0", now);
  staggeredRollout(startAt, endAt, stages, "fodd1", now+1000);
  staggeredRollout(startAt, endAt, stages, "fdo2", now+2000);
  staggeredRollout(startAt, endAt, stages, "aoo3", now+3000);
  staggeredRollout(startAt, endAt, stages, "foo4", now+4000);
  staggeredRollout(startAt, endAt, stages, "aoc5", now+5000);
  staggeredRollout(startAt, endAt, stages, "foo6", now+6000);
  staggeredRollout(startAt, endAt, stages, "bo7", now+7000);
  staggeredRollout(startAt, endAt, stages, "foo8", now+8000);
  staggeredRollout(startAt, endAt, stages, "foo9", now+9000);
  staggeredRollout(startAt, endAt, stages, "foo10", now+10000);
  staggeredRollout(startAt, endAt, stages, "foo11", now+11000);
  
}

test();