Question

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Object comparison in JavaScript

Is there any method that takes in 2 JSON objects and compares the 2 to see if any data has changed?

Edit

After reviewing the comments, some clarification is needed.

1. A JSON object is defined as

   “an unordered set of name/value pairs.
   An object begins with { (left brace)
   and ends with } (right brace). Each
   name is followed by : (colon) and the
   name/value pairs are separated by ,
   (comma).” — json.org

2. My goal is to be able to compare 2 JSON object literals, simply put.

I am not a javascript guru so if, in javascript, these are object literals, then I suppose that’s what I should call them.

I believe what I am looking for is a method capable of:

1. Deep recursion to find a unique name/value pair
2. Determine the length of both object literals, and compare the name/value pairs to see if a discrepancy exists in either.

Answer 1

Simply parsing the JSON and comparing the two objects is not enough because
it wouldn’t be the exact same object references (but might be the same values).

You need to do a deep equals.

From http://threebit.net/mail-archive/rails-spinoffs/msg06156.html – which seems the use jQuery.

Object.extend(Object, {
   deepEquals: function(o1, o2) {
     var k1 = Object.keys(o1).sort();
     var k2 = Object.keys(o2).sort();
     if (k1.length != k2.length) return false;
     return k1.zip(k2, function(keyPair) {
       if(typeof o1[keyPair[0]] == typeof o2[keyPair[1]] == "object"){
         return deepEquals(o1[keyPair[0]], o2[keyPair[1]])
       } else {
         return o1[keyPair[0]] == o2[keyPair[1]];
       }
     }).all();
   }
});

Usage:

var anObj = JSON.parse(jsonString1);
var anotherObj= JSON.parse(jsonString2);

if (Object.deepEquals(anObj, anotherObj))
   ...