[рони]

на строке a = s[0];

var arr = [
{key:1, val:123, val2:1},
{key:2, val:223, val2:2},
{key:3, val:323, val2:2},
{key:4, val:423, val2:1}
], obj = {}, a,b;
Object.keys(arr).forEach(function (a) {
  var el = arr[a];
  obj[el.key] = [el.val,el.val2];
});

  var s = obj[1];
  a = s[0];
  b = s[1];
 alert(a+ " - " + b)