Array text to numbers, find matching values and sort

Example Fiddle

Step 1 is fairly easy by using javascript's join and split methods respectively:

var arr = carArray .join().split(',');

For step 2, several methods can be used, the most common one using an object and using the elements themselves as properties. Since you only need to get the most occurring value if there is a reoccurring value, it can be used in the same loop:

var counts = {}; //object to hold count for each occurence    
var max = 0, maxOccurring;
arr.forEach(function(el){     
    var cnt = (counts[el] || 0); //previous count
    counts[el] = ++cnt;
    if(cnt > max && cnt > 1){ //only register if more than once (cnt>1)
        max=cnt;
        maxOccurring = el;
    }
});

After the above, the variable maxOccurring will contain the reoccurring value (if any) and max will contain the times it occured

For step 4 the easiest way is to loop through the compare array and get the element that occurs in the input array:

var cmpArr = ['6','7','4','1','2','8','9','5'];
//find the first occurrence inside the cmpArr

res = function(){ for(var i= 0 ; i < cmpArr.length; i++){ if(arr.indexOf(cmpArr[i]) !== -1)return cmpArr[i];}}();  

The above uses an in place function which is called immediately to be able to use return. You could also just use a loop and assign res when found, then break from the loop.

Last update, an alternate fiddle where the above is converted to a single function: http://jsfiddle.net/v9hhsdny/5/

Well first of all the following code results in four matching answers since the jQuery selectors are the same.

var questionAnswer1 = $(this).find('input[name=questionText]').val();
var questionAnswer2 = $(this).find('input[name=questionText]').val();
var questionAnswer3 = $(this).find('input[name=questionText]').val();
var questionAnswer4 = $(this).find('input[name=questionText]').val();

var carArray = [questionAnswer1, questionAnswer2, questionAnswer3, questionAnswer4];

You could use the eq(index) method of jQuery to select the appropriate element. However having 4 inputs with the same name is a bad practice.

Well lets say that the carArray has 4 different values which all consist out of comma separated numbers. You could then do the following:

var newArr = [];
carArray.forEach(function(e) {
    e.split(",").forEach(function(n) {
        newArr.push(n);
    });
});

Well then we got to find the most occurring number. JavaScript doesn't have any functions for that so we will have to find an algorithm for that. I found the following algorithm on this stackoverflow page

var count = function(ary, classifier) {
    return ary.reduce(function(counter, item) {
        var p = (classifier || String)(item);
        counter[p] = counter.hasOwnProperty(p) ? counter[p] + 1 : 1;
        return counter;
    }, {})
}

var occurances = count(newArr);

It isn't clear to me what you're trying to do in step 3 and 4, so can't answer those at the moment.

var ary = ["1,8", "4,6,8", "8,9", "6,9"];

var splitted = ary.reduce(function(acc, item) {
        return acc.concat(item.split(','));
    }, []);

var occurences = splitted.reduce(function(acc, item) {
        if (!acc.hasOwnProperty(item)) acc[item] = 0;
        acc[item] += 1;
        return acc;
    },{}),
    biggest = Object.keys(occurences).reduce(function (acc, key) {
        if (occurences[key] > acc.occurences) {
            acc.name = key;
            acc.occurences = occurences[key];
        }
        return acc;
    },{'name':'none','occurences':0}).name;

var vals=["1,8", "4,6,8", "8,9", "6,9"];
// 1)  turn into number array
var arrNew=[];
for(var i=0; i<vals.length; i++)   
{ 
    arrLine=vals[i].split(",");
    for (var j=0;j<arrLine.length;j++) { arrNew.push (parseInt(arrLine[j])) }
}

//result: 
alert(arrNew.join(";");

// 2) find most common
var found=[];
for(var i=0; i<arrNew.length; i++) {
    // make an array of the number of occurrances of each value
    if (found["num"+newArray[i]]) {
        found["num"+newArray[i]] ++ ;
    } else {
        found["num"+newArray[i]]=1;
    }
}

var mostCommon={count:0,val:"ROGUE"};
for (x in found) {
    if (found[x] > mostCommon.count) {
        mostCommon.count=found[x].count;
        mostCommon.val=x;
    }
}

// result : 
alert(mostCommon.val);

//3) not quite sure what you meant there

// 4) unique values:
// at this point the 'found' list contains unique vals
var arrUnique=[];
for (x in found) {
    arrUnique.push[x];
}
// result :
alert(arrUnique.join(";"))


//sort:
arrUnique.sort(function(a, b){return a-b}); 

(This won't work in most browsers) but on a side note, when ES6 becomes widely supported, your solution could look like this:

var arr1 = ["1,8", "4,6,8", "8,9", "6,9"];
var arr2 = arr1.join().split(',');
var s = Array.from(new Set(arr2)); //Array populated by unique values, ["1", "8", "4", "6", "9"]

Thought you might like to see a glimpse of the future!

1.

var orgArray = ['1,8', '4,6,8', '8,9', '6,9'];
var newArray = [];
for (var i in orgArray) {
  var tmpArray = orgArray[i].split(',');
  for (var j in tmpArray) {
    newArray.push(Number(tmpArray[j]));
  }
}

2.

var counts = {};
var most = null;
for (var i in newArray) {
  var num = newArray[i];
  if (typeof counts[num] === 'undefined') {
    counts[num] = 1;
  } else {
    ++(counts[num]);
  }
  if (most == null || counts[num] > counts[most]) {
    most = num;
  } else if (most != null && counts[num] === counts[most]) {
    most = null;
  }
}

I don't understand the question 3 and 4 (what "unique order" means) so I can't answer those questions.