JSFiddle - React, Tailwind, and code Playground

JavaScript

var uniqueInput = {
                           "country": "UK",
                           "firstname": "Calvin",
                           "lastname": "Borders",
                           "address1": "2201 N Pershing Dr",
                           "address2": "Apt 417",
                           "city": "Arlington",
                           "state": "VA",
                           "zip": "22201"
                           
                            };
var duplicatedInput = {
                           "country": "US",
                           "firstname": "Kevin",
                           "lastname": "Borders",
                           "address1": "2201 N Pershing Dr",
                           "address2": "Apt 417",
                           "city": "Arlington",
                           "state": "VA",
                           "zip": "22201"
                           
                            };

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"
                            }];

function checkDuplicate(checkTarget,source){
    _.each(source,function(obj){
        if(_.isEqual(checkTarget,obj)){ 
            alert("duplicated");
        }
   ...