Q:

Pushing data to object/array for later comparison

I'm trying to store strings in a object/array for later comparison.  I have no idea if my approach is correct. 

The idea:
I'll be using the data to compare if there's been changes in the HTML where the strings are from.  If there are changes the script is gonna send a notification with information on what changes there is. 

So I have a function that needs to push data into either an object or an array.  I need to store the data for later use, where I need to compare if there's any changes.  It's specifically a scheme of classes. 

An example of what the object/array is gonna look after the data is injected:
    obj = 
    {
      "mon": { 
              0:{date:date, info:info, class:class}
              1:{date:date, info:info, class:class}
              2:{date:date, info:info, class:class}
             },
      "tue": {...},
      "...":
    }

And so on... So the object/array is gonna contain data for every class, for every day. 
I need to be able to compare the stored obj.mon.0 with the new obj.mon.0, as an example. 
So my question is:

What's the best approach, in an object as above, or in a array? 
How do I go about storing information in the object/array for every class, on every day? 
And is this even the easiest approach for this context? 

Thank you for your time. 

A:

Array is probably the best to choose here. 
and you can keep the date, info and class as object. 
Please share your suggestions too.