Sorting mongodb by reddit ranking algorithm

Question

Here is a js code to rank items according to Reddit\'s ranking algorithm.

My question is: how do I use this code to rank my mongodb documents ?

(Reddit\'s ra

Answer 1

Theres a problem with your function:

new Date(1970, 1, 1) // Sun Feb 01 1970 00:00:00 GMT-0300 (BRT)

Yep, month 1 is February, and it uses the systems timezone as well. Epoch in JavaScript is

var epoch = new Date(Date.UTC(1970, 0, 1))

Since

epoch.getTime() // 0

The function

function epochSeconds(d){
    return (d.getTime() - new Date(1970,1,1).getTime())/1000;
}

should be just

function epochSeconds(d){
    return d.getTime()/1000;
}

Compressing a bit, this returns exactly the same results as the python function in http://amix.dk/blog/post/19588

function hot (ups, downs, date){
  var score = ups - downs;
  var order = Math.log(Math.max(Math.abs(score), 1)) / Math.LN10;
  var sign = score > 0 ? 1 : score < 0 ? -1 : 0;
  var seconds = (date.getTime()/1000) - 1134028003;
  var product = order + sign * seconds / 45000;
  return Math.round(product*10000000)/10000000;
}