How to iterate javascript object properties in the order they were written.

Question

Hi. I identified a bug in my code which I hope to solve with minimal refactoring effort. This bug occurs in Chrome and Opera browsers. Problem:

var obj = {23:"AA",12:"BB"};
//iterating through obj's properties
for(i in obj)
  document.write("Key: "+i +" "+"Value: "+obj[i]);

Output in FF,IE Key: 23 Value: AA Key: 12 Value: BB

Output in Opera and Chrome (Wrong)
Key: 12 Value BB
Key: 23 Value AA

I attempted to make an inverse ordered object like this

var obj1={"AA":23,"BB":12};
for(i in obj1)
  document.write("Key: "+obj[i] +" "+"Value: "+i);

However the output is the same. Is there a way to get for all browser the same behaviour with small changes?

Answer 1

No. JavaScript Object properties have no inherent order. It is total luck what order a for...in loop operates.

If you want order you'll have to use an array instead:

var map= [[23, 'AA'], [12, 'BB']];
for (var i= 0; i<map.length; i++)
    document.write('Key '+map[i][0]+', value: '+map[i][1]);

Answer 2

I think you'll find the only reliable way to do this would be to use an array rather than an associative array, eg:

var arr = [{key:23,val:"AA"},{key:12,val:"BB"}];
for(var i=0; i<arr.length; i++)
  document.write("Key: "+arr[i].key +" "+"Value: "+arr[i].val);