Merge 2 JSON strings??

I have the following function, that is merging 2 JSON strings.  It's working for the most part, except that It's not currently handling adjacent properties of each object.

So, for example in the code below, the first object has an Address object with several properties, and the second object has that same Address object with different properties.

Currently, the properties of the first object are getting overriden, instead of merged.

If the properties are the same in both objects, then they can be overridden (no duplicates), but if they're different, then I'd like them to be appended...is this simple ??

var firstObj = { "Type":"1", "Company": {"CompanyAddresses":[ {"Address": {"PostalCode":"V6H1S2", "AddressLine1":"3318 Main"}}]} };
                var secondObj = { "Type":"1", "Company": {"CompanyAddresses":[ {"Address": {"AddressLine2":"#2"}}]} }
                //var secondObj = { "ContractorName":"My Name", "Company": {"Name":"My Company Rocks"} };
                function merger(a,b)
                {
                    for( i in a )
                    {
                            for( j in b )
                            {
                                    if(i==j)
                                    {
                                            for( k in b[j] )
                                            {
                                                    a[i][k] = b[j][k];
                                            }
                                    }
                            }
                    }
                }
                merger(firstObj,secondObj);
                alert(firstObj.Company.CompanyAddresses[0].Address.AddressLine1);

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