Add only unique objects to an array in JavaScript

Question

Let's say I start with this:

var shippingAddresses = [
    {
      "firstname": "Kevin",
      "lastname": "Borders",
      "address1": "2201 N Pershing Dr",
      "address2": "Apt 417",
      "city": "Arlington",
      "state": "VA",
      "zip": "22201",
      "country": "US"
    }, 
    {
      "firstname": "Dan",
      "lastname": "Hess",
      "address1": "304 Riversedge Dr",
      "address2": "",
      "city": "Saline",
      "state": "MI",
      "zip": "48176",
      "country": "US"
    }
]

I use this to prepopulate a form.
Users can edit entries or add new ones. I need to prevent them from adding duplicates.

The issue is that the structure of the form that I am serializing and the order these values are returned from the database are not the same, so there is a chance that I will insert an item into this array with the following format:

{
  "country": "US",
  "firstname": "Kevin",
  "lastname": "Borders",
  "address1": "2201 N Pershing Dr",
  "address2": "Apt 417",
  "zip": "22201",                                    
  "city": "Arlington",
  "state": "VA"
}

Which is the same as the first entry, just ordered differently.

I am loading underscorejs, so if there's a way to handle it with that library that would be great. I'm also using jQuery if that helps.

At this point I'm not sure how to proceed.

Answer 1

The Underscore findWhere function does exactly what you need - it's not an indexOf search by object identity, but searches objects whose properties have the same values as the input.

if (_.findWhere(shippingAddresses, toBeInserted) == null) {
    shippingAddresses.push(toBeInserted);
}

Answer 2

Basic example using lodash union method:

var a = [1,2,3];

// try to add "1" and "4" to the above Array
a = _.union(a, [1, 4]);

console.log(a);

<script src="//cdnjs.cloudflare.com/ajax/libs/lodash.js/4.13.1/lodash.min.js"></script>

While this doesn't directly answers the question, it does answers the broader question of how to add unique values to an Array, and like myself, others might stumble upon this page from google.