title: Selectize.js get more data in "onItemAdd" callback
body: <p><strong>TL;DR</strong></p>
  
  <p>To make it clearer, I want to have access to ALL the data in the selected JSON object inside the <code>onItemAdd</code> function. Right now I only have access to <code>_id</code> and <code>name</code> via the config variables. </p>
  
  <hr>
  
  <p>Ok, so I have a working Selectize.js function grabbing a JSON object from my server and creating the select options. </p>
  
  <p>What I want to know is, can I get anymore data from the existing JSON object inside the "onItemSelect" callback?</p>
  
  <p>The only data I can get directly is the <code>value</code> as specified in the config, which in this case is the "_id" and the <code>$item</code> which i assume is form the <code>labelField</code> in the config, in this case is the <code>name</code> form the JSON data.</p>
  
  <p>How can I get more data than that for the selected item? You see in the render object I use the variable <code>item.sku</code>, how can I access the <code>sku</code> variable in the "onItemAdd" callback?</p>
  
  <p>the data form the server is a json array:</p>
  
  <pre><code>[
    { _id: 'abcd1234', name: 'Sample', sku: '00123' }, 
    { _id: 'efgh5678', name: 'Sample2', sku: '00124' }
  ]
  </code></pre>
  
  <p>My function</p>
  
  <pre><code>// setup select box to add new products to list
  $('#buyingGroupAddProducts').selectize({
    valueField: '_id',
    labelField: 'name',
    searchField: 'name',
    options: [],
    create: false,
    closeAfterSelect: true,
    render: {
      option: function(item, escape) {
        return '&lt;div&gt;'+ escape(item.sku) + ': ' + escape(item.name) + '&lt;/div&gt;';
      }
    },
    load: function(query, callback) {
      if (!query.length) return callback();
      $.ajax({
        url: '/buying/products-search',
        type: 'GET',
        dataType: 'json',
        data: {
          q: query
        },
        error: function() {
          callback();
        },
        success: function(res) {
          callback(res);
        }
      });
    },
    onItemAdd: function(value, $item) {
  
      // DO the thing
      console.log($item);
  
    }
  });
  </code></pre>
  
  <p>SelectizeJS site: <a href="http://selectize.github.io/selectize.js/" rel="nofollow">http://selectize.github.io/selectize.js/</a></p>