How to get the most frequent item (number or string) in an array?

Question

I am trying to get the most frequent item in a javascript array builded by a Dialogflow chatbot with the fullfilment code. However if I can display the array, it seems the function I tried doesn't work well to find the most frequent item:

const functions = require('firebase-functions');
const {WebhookClient} = require('dialogflow-fulfillment');
const {Card, Suggestion} = require('dialogflow-fulfillment');
var answers = [];

process.env.DEBUG = 'dialogflow:debug'; // enables lib debugging statements

exports.dialogflowFirebaseFulfillment = functions.https.onRequest((request, response) => {
  const agent = new WebhookClient({ request, response });
  console.log('Dialogflow Request headers: ' + JSON.stringify(request.headers));
  console.log('Dialogflow Request body: ' + JSON.stringify(request.body));

  function welcome(agent) {
    agent.add(`Welcome to my agent!`);
  }

  function fallback(agent) {
    agent.add(`I didn't understand FULLFILMENT`);
    agent.add(`I'm sorry, can you try again? FULLFILMENT`);
  }

  function rhymingWordHandler(agent){
    agent.add('Intent called');
  }

  function answer1Handler(agent){
    agent.add('Intent answer1 called');
    const answer = agent.parameters.number;
    answers.push(answer);
  }

  function answer2Handler(agent){
    agent.add('Intent answer2 called');
    const answer = agent.parameters.number;
    answers.push(answer);
  }

  function answer3Handler(agent){
    agent.add('Intent answer3 called');
    const answer = agent.parameters.number;
    answers.push(answer);
    agent.add('Here is the mode');
    const mfi = mode(answers);
    agent.add(mfi.toString());
  }

  function mode(arr1){
    var mf = 1; //default maximum frequency
    var m = 0;  //counter
    var item;  //to store item with maximum frequency
    for (var i=0; i<arr1.length; i++)    //select element (current element)
    {
            for (var j=i; j<arr1.length; j++)   //loop through next elements in array to compare calculate frequency of current element
            {
                    if (arr1[i] == arr1[j])    //see if element occurs again in the array
                     m++;   //increment counter if it does
                    if (mf<m)   //compare current items frequency with maximum frequency
                    {
                      mf=m;      //if m>mf store m in mf for upcoming elements
                      item = arr1[i];   // store the current element.
                    }
            }
            m=0;   // make counter 0 for next element.
    }
    return item;
  }

  // Run the proper function handler based on the matched Dialogflow intent name
  let intentMap = new Map();
  intentMap.set('Default Fallback Intent', fallback);
  intentMap.set('RhymingWord', rhymingWordHandler);
  intentMap.set('answer1', answer1Handler);
  intentMap.set('answer2', answer2Handler);
  intentMap.set('answer3', answer3Handler);

  agent.handleRequest(intentMap);
});

My input are 1,2 and 1. So the array is [1,2,1], it should output 1. I guess my mode function doesn't work for numbers? How can I make it versatile?

I followed this answer, it should have been allright.

You'll have a bad time with a global `answers` array; it would be shared between all clients of your bot. Unless that's what you want to do, of course... — AKX, Apr 27 '20 at 13:17
@AKX Ho, no. Of course not, I would like each to be specific to each client — Revolucion for Monica, Apr 27 '20 at 13:55

score 2 · Answer 1 · answered Apr 27 '20 at 13:23

Something like this ought to work for your mode function:

function mode(arr) {
  const counts = {};
  let maxCount = 0;
  let maxKey;
  // Count how many times each object (or really its string representation)
  // appears, and keep track of the highest count we've seen.
  for (let i = 0; i < arr.length; i++) {
    const key = arr[i];
    const count = (counts[key] = (counts[key] || 0) + 1);
    if (count > maxCount) {
      maxCount = count;
      maxKey = key;
    }
  }
  // Return (one of) the highest keys we've seen, or undefined.
  return maxKey;
}

score 2 · Answer 2 · answered Jun 05 '22 at 00:26

2

Here is an ES6 version.

function mode(arr) {
  const store = {}
  arr.forEach((num) => store[num] ? store[num] += 1 : store[num] = 1)
  return Object.keys(store).sort((a, b) => store[b] - store[a])[0]
}

answered Jun 05 '22 at 00:26

gazanther

41
1
3

Please add supporting details to your answer to improve it. – Ethan Jun 06 '22 at 14:59

How to get the most frequent item (number or string) in an array?

2 Answers2