Reference Javascript Array (JSON Format) with unknown array key

How would you reference a value in a Javascript object without the key?

So, given the object:

var JSONdata= [ 
    {"index":"1","var1":1,"var2":2}, 
    {"index":"2","var1":3,"var2":2}, 
    {"index":"3","var1":3,"var2":1}, 
    {"index":"4","var1":2,"var2":1}, 
    {"index":"5","var1":1,"var2":3}, 
]; 

Say I want to reference the values of var1 and var2 in a loop, but the names "var1" and "var2" change and the number of variables also changes.

So in Pseudocode:

while ( i < JSONdata.leng开发者_运维技巧th ) {
   for (j = 1 to Num_variables) {
       Give me the value for varN
   next j
   }
i++
}

Thanks

---

var JSONdata= [ 
  {"index":"1","var1":1,"var2":2}, 
  {"index":"2","var1":3,"var2":2}, 
  {"index":"3","var1":3,"var2":1}, 
  {"index":"4","var1":2,"var2":1}, 
  {"index":"5","var1":1,"var2":3}
]; 

var fields=[
  "var1",
  "var2"
];

for(var i=0, ii=JSONdata.length; i<ii; i++){
  for(var j=0, jj=fields.length; j<jj; j++){
    $('#hello').html($('#hello').html()+' '+JSONdata[i][fields[j]]);
  }
  $('#hello').html($('#hello').html()+' '+'<br/>');
}

see there http://jsbin.com/ufege4/edit

---

The obj.propertyName notation in JavaScript is syntactic sugar for obj['propertyName'] -- So, you can access your vars using: JSONData[i]['var'+j];