Ionic Wordpress JSON API vs WP Rest API 2

I'm trying to parse the image_gallery which can be obtained from WP REST API 2 but not JSON API. I'm using ionWordpress template for Ionic to get data from Wordpress and it's already coded for getting data with JSON API.

Here's the JSON data parsed from JSON API

  "posts": [
    {
      "id": 383,
      "type": "event",
      "slug": "motorcross-challenge",
      "url": "http://www.brunei.events/brunei/event/motorcross-challenge/",
      "custom_fields": {
        "event_type": [
          "Regular event"
        ],
        "zooming_factor": [
          "17"
        ],
        "address": [
          "Motorcross Track, Tutong, Tutong District, Brunei"
        ],
        "geo_latitude": [
          "4.8243656000000135"
        ],
        "geo_longitude": [
          "114.66116149999993"
        ],
        "map_view": [
          "Road Map"
        ],
        "featured_type": [
          "none"
        ],
        "featured_h": [
          "n"
        ],
        "featured_c": [
          "n"
        ],
        "country_id": [
          "32"
        ],
      },
    }

Here's the data from WP Rest Api 2

{
    "featured_img": false,
    "image_gallery": [
      "http://www.brunei.events/wp-content/uploads/2017/12/WhatsAppImage20171117at4.34.19PM1512704778.jpeg"
    ],
    "html_var": {
      "package_id": "49",
      "package_name": "Free",
      "post_city_id": "4",
      "end_time": "21:30",
      "st_time": "19:30",
      "end_date": "2017-12-17",
      "st_date": "2017-12-15",
      "event_type": "Regular event",
      "map_view": "Road Map",
    }
  }

Yes I notice that both are not the same, it's just an example to show that with WP Rest API, it gets the image_gallery but not in JSON API. Is there a workaround to get this in JSON API. Do I have to modify the code in JSON API?

Thanks in advance!