updateScore = function (args) { var collection = args.collection; var item = args.item; var forceUpdate = args.forceUpdate; // console.log(item) // Status Check if (!!item.status && item.status !=2) // if item has a status and is not approved, don't update its score return 0; // Age Check // If for some reason item doesn't have a "postedAt" property, abort if (!item.postedAt) return 0; var postedAt = item.postedAt.valueOf(); var now = new Date().getTime(); var age = now - postedAt; var ageInHours = age / (60 * 60 * 1000); if (postedAt > now) // if post has been scheduled in the future, don't update its score return 0; // For performance reasons, the database is only updated if the difference between the old score and the new score // is meaningful enough. To find out, we calculate the "power" of a single vote after n days. // We assume that after n days, a single vote will not be powerful enough to affect posts' ranking order. // Note: sites whose posts regularly get a lot of votes can afford to use a lower n. // n = number of days after which a single vote will not have a big enough effect to trigger a score update // and posts can become inactive var n = 30; // x = score increase amount of a single vote after n days (for n=100, x=0.000040295) var x = 1/Math.pow(n*24+2,1.3); // time decay factor var f = 1.3; // use baseScore if defined, if not just use the number of votes // note: for transition period, also use votes if there are more votes than baseScore // var baseScore = Math.max(item.votes || 0, item.baseScore || 0); var baseScore = item.baseScore; // HN algorithm var newScore = baseScore / Math.pow(ageInHours + 2, f); // console.log(now) // console.log(age) // console.log(ageInHours) // console.log(baseScore) // console.log(newScore) // Note: before the first time updateScore runs on a new item, its score will be at 0 var scoreDiff = Math.abs(item.score - newScore); // only update database if difference is larger than x to avoid unnecessary updates if (forceUpdate || scoreDiff > x){ collection.update(item._id, {$set: {score: newScore, inactive: false}}); return 1; }else if(ageInHours > n*24){ // only set a post as inactive if it's older than n days collection.update(item._id, {$set: {inactive: true}}); } return 0; };