user an array of key names to verify that they're in an object, add empty array with key 0 if false

checker.js

    var checker = ['attain-location-address-1', 'attain-location-address-2', 'attain-location-city', 'attain-location-state', 'attain-location-zipcode']
        for (var i = 0; i < checker.length; i++) {
            if (!result['custom_fields'].hasOwnProperty(checker[i])) {
                result['custom_fields'][checker[i]] = [];
                result['custom_fields'][checker[i]][0] = '';
            }
        }
        return result;