How to insert new child data in Firebase web app?
<p>I am building a simple car database app. When a user adds a new car it creates the below JSON data with blank fields for the gallery:</p>

<pre><code>{
    "name": "Cars",
    "gallery": [{
        "img": "http://",
        "title": "BMW"
    }, {
        "img": "http://",
        "title": "Lexus"
    }, {
        "img": "http://",
        "title": "Ferrari"
    }],
    "pageId": "23",
    "storeURL": "/app/cars/gallery"
}
</code></pre>

<p>Now what I want to do in the app is if a user adds a new gallery image it should add new child after the last gallery picture. So after <strong>Ferrari</strong> it should insert a new object. I cannot seem to do this as every tutorial leads to a dead end and also the official Google docs specify that <code>set()</code> will replace all data so if you use <code>update()</code> it will add and in this case it does not add.</p>

<p>This code deletes all data:</p>

<pre><code>function add(){
  var data = [
    {
      title: 'Mercedes',
      img: 'http://'
    }
  ]
  var postData = {
    pageGallery: data
  };
  var updates = {};
  updates['/app/cars/'] = postData;
  firebase.database().ref().update(updates);
  console.log('New car added');

}
</code></pre>

<p>And if I change and add the child:</p>

<pre><code>firebase.database().ref().child('gallery').update(updates);
</code></pre>

<p>It does not do anything to do the data. Please can you help?</p>