How to pivot a javascript array

Question

I have this javascript array:

[['a', 'x', 1],
 ['a', 'y', 2],
 ['b', 'x', 3],
 ['b', 'z', 4],
 ['c', 'y', 5],
 ['c', 'z', 6]]

How do I pivot it to something like below with the 2nd column ('x', 'y', 'z') from above going across.

[['a', 1, 2, null],
 ['b', 3, null, 4],
 ['c', null, 5, 6]]

EDIT: Sorry I was unclear. The answers so far seem to be referencing a static length/value for x, y, z. The array will be dynamic and can have anything in the 2nd column (ex. 't','u','v','w' instead of 'x','y','z'). I think I need to fill the array up first with nulls for all the possible combinations and then push in the values.

Thanks..

Answer 1

Going by Fabricio's comment, here is how you can accomplish something similar:

var result = {};
for(var i=0;i< basearray.length;i++){
    if(!result[basearray[i][0]]){
        result[basearray[i][0]]={};
    }
    result[basearray[i][0]][basearray[i][1]]=basearray[i][2];
}

Note that this returns an object or hashmap, not strictly an array, but the data is more organised and it can easily be turned into an array if you so wish. Here is a demonstration (check your console).

By adding this code:

var count=0;
for(var key in result){
    result[count]=[];
    result[count][0]=key;
    result[count][1]=result[key].x||null;
    result[count][2]=result[key].y||null;
    result[count][3]=result[key].z||null;
    count++;
}

your result object now simulates both structures, your original array of arrays, and the suggested key value pairs. You can see the results here: http://jsfiddle.net/9Lakw/3/

Here is what result looks like:

{
   "a":{
      "x":1,
      "y":2
   },
   "b":{
      "x":3,
      "z":4
   },
   "c":{
      "y":5,
      "z":6
   },
   "0":[
      "a",
      1,
      2,
      null
   ],
   "1":[
      "b",
      3,
      null,
      4
   ],
   "2":[
      "c",
      null,
      5,
      6
   ]
}

Answer 2

Here's how I'd do it, with arrays and null fillers as in the question. This assumes that coords for given points always come in succession.

var arr = [['a', 'x', 1],
 ['a', 'y', 2],
 ['b', 'x', 3],
 ['b', 'z', 4],
 ['c', 'y', 5],
 ['c', 'z', 6]];

var aux = {
        x: 1,
        y: 2,
        z: 3
    },
    output = [],
    lastItem,
    currItem;

for (var i = 0; i < arr.length; i++) {
    currItem = arr[i];
    if (currItem[0] !== lastItem) {
        lastItem = currItem[0];
        output.push([lastItem, null, null, null]);
    }
    output[output.length-1][aux[currItem[1]]] = currItem[2];
}
console.log(output); //[["a", 1, 2, null], ["b", 3, null, 4], ["c", null, 5, 6]]

Fiddle