Question

I have 2 arrays with the following data:

Array1 = [A, A, A, A, B, B, B, C, C, C, C, C];    
Array2 = [4, 2, 4, 6, 3, 9, 6, 5, 4, 6, 2, 8];

I want to create 2 new arrays from these values:

Array3 = [A, B, C];    
Array4 = [4, 6, 5];

The values in Array 4 are the averages from Array2.

How should the javascript or jquery code look like to create Array3 and Array4?

edit:

I would like to group the values like this:

Array1      Array2
  A           2
  A           4
------------------
  B           2
  B           6
------------------
  C           3
  C           6
  C           9

     result:

Array3      Array4
  A           3          Average from 2 and 4
  B           4          Avarage from 2 and 6
  C           6          Average from 3, 6 and 9

Answer 1

Try

// Your initial Variables
Array1 = ['A', 'A', 'A', 'A', 'B', 'B', 'B', 'C', 'C', 'C', 'C', 'C'];    
Array2 = [4, 2, 4, 6, 3, 9, 6, 5, 4, 6, 2, 8];

// a temporary variable where we store our progress
var groups = {}

$.each(Array1, function(index,item){
    if (!groups[item]){
        groups[item] = {sum:0, count:0};
    }
    groups[item].sum += Array2[index]; // sum values belonging to same key 
    groups[item].count++; // increase counter of values per key
});

// create the letter only array
var Array3 = $.map(groups,function(value,key){
    return key;
});
// create the averages array
var Array4 = $.map(groups,function(value,key){
    return value.sum / value.count;
});

// show the results
console.log(Array3, Array4);