javascript - Find the most frequent item of an array (not just strings)

Question

Can someone walk me through this exercise? Write a JavaScript program to find the most frequent item of an array.

var arr1 = [3, 'a', 'a', 'a', 2, 3, 'a', 3, 'a', 2, 4, 9, 3];
var mf = 1;
var m = 0;
var item;

for (var i = 0; i < arr1.length; i++) {
  for (var j = i; j < arr1.length; j++) {
    if (arr1[i] == arr1[j]) m++;
    if (mf < m) {
      mf = m;
      item = arr1[i];
    }
  }

  m = 0;
}

alert(item + " ( " + mf + " times ) ");

Answer 1

User want's explanation of the code:

Here they select the 1st element of the array and compare it with every element then on.

Then they increment the counter m every time the same elements occur again, frequency of that element.

Also a variable mf is kept to keep track of maximum frequency. Compare the elements frequency with maximum frequency and update item and mf as per present element's frequency.

var arr1=[3, 'a', 'a', 'a', 2, 3, 'a', 3, 'a', 2, 4, 9, 3]; //array
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.
}