How would you count top repetitions in a stream (grouping and summing similar strings too)

I'm answering my question. This is just a suggestion of course, I assume same problem could be approached differently.

First I discovered Bloom Filters which is a probabilistic hash, very useful for endless streams (not to blow memory), to be able to discover repetitions.

One particular algorithm based on Bloom Filters is topK

Practically, as I'm running on node I came up with the following solution with some other constraints (refresh the learning bag when half the queue is seen already). Also, purge elements earlier than one month on insertions (it could be triggered otherwise).

Also I used a circular queue for the one month only scan.

const { TopK } = require('bloom-filters')
const FuzzySet = require('fuzzyset')


var adt_1 = require("@toreda/adt")

// generate random strings 
function makeid(length) {
  var result = '';
  var characters = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789';
  var charactersLength = characters.length;
  for (var i = 0; i < length; i++) {
    result += characters.charAt(Math.floor(Math.random() *
      charactersLength));
  }
  return result;
}
// arbitrary choice
const maxSize = 3000
var circularBuffer = new adt_1.CircularQueue({
  maxSize: maxSize,
  overwrite: true
})

let pushCount = 0
const isHalfSeen = () => ((pushCount++) % maxSize) > maxSize / 2
const purgeOld = () => {
  const front = circularBuffer.front()
  if (front && front.when < new Date().getTime() - 2592000000 /*month*/) {
    circularBuffer.pop()
    purgeOld()
  } else {
    return
  }
}
let fuzzyset = FuzzySet()
const checkSimilarity = (keyword) => {
  const similar = fuzzyset.get(keyword)
  if (!similar || (similar[0][0] < 0.8)) {
    fuzzyset.add(keyword)
    return false
  } else {
    return similar[0][1]
  }
}

const refreshTopK = (keyword) => {
  purgeOld()
  const similar = checkSimilarity(keyword)
  if (similar)
    keyword = similar
  circularBuffer.push([new Date().getTime(), keyword])
  // when half the queue is seen already
  // renew the topK bag
  if (isHalfSeen()) {
    console.log(('isHalfSeen'))
    // print the top search keywords so far
    for (let item of topk.values()) {
      console.log(`Item "${item.value}" is in position ${item.rank} with an estimated frequency of ${item.frequency}`)
    }
    pushCount = 0
    topk = new TopK(10, 0.001, 0.99)
    circularBuffer.forEach((elem, index, arr) => {
      topk.add(elem[1])
    })
  }
}

for (let index = 0; index < 10000; index++) {
  refreshTopK(makeid(5))
}