jQuery Simple Example

HTML

<script src="//www.addressfinder.co.nz/assets/v2/widget.js"></script>
<label for="search_field">Address</label>
<input type='text' class='address_field' />

CSS

body {
    padding: 5px;
}

label {
    font-weight: bold;
}

input[type=text] {
    width: 20em
}

p {
    margin: 1em 0 0;
}

JavaScript

$(document).ready(function() {
  var orig = [{
        "id": "Test",
        "parent": "#"
    }, {
        "id": "Test1",
        "parent": "Test"
    }, {
        "id": "Test2",
        "parent": "Test"
    }, {
        "id": "Test3",
        "parent": "Test2"
    }, {
        "id": "Test4",
        "parent": "Test1"
    }, {
        "id": "Test5",
        "parent": "Test1"
    }, {
        "id": "Test6",
        "parent": "Test4"
    }];
    
    
    function getChildren(id){
      let result = [];
      $.each(orig, function(i, d) {
         if (d.parent === id) {
         		result.push(d);
            result.push(...getChildren(d.id));
         }
      });
      return result;
    }

    console.log(getChildren('Test'));
});