select2/docs/_includes/options/data/select.html

<section>
  <h2 id="data-adapters-select-tag">
    Can Select2 be used with a <code>&lt;select&gt;</code> tag?
  </h2>

  <h3>
    Does Select2 support nesting options?
  </h3>

  <p>
    Yes, just like in a standard <code>select</code>.
  </p>

  <h3>
    How many levels of nesting can there be?
  </h3>

  <p>
    Only a single level of nesting is allowed per the HTML specification.
  </p>

  <h3>
    Can <code>&lt;optgroup&gt;</code> tags be made selectable?
  </h3>

  <p>
    No. This is a limitation of the HTML specification and is not a limitation that Select2 can overcome.
  </p>

  <h3>
    How are <code>&lt;option&gt;</code> and <code>&lt;optgroup&gt;</code> tags serialized into data objects?
  </h3>

  <p>
    Select2 will convert the <code>&lt;option&gt;</code> tag into a data object based on the following rules.
  </p>

<pre class="prettyprint linenums">
{
  "id": "value attribute" || "option text",
  "text": "label attribute" || "option text",
  "element": HTMLOptionElement
}
</pre>

  <p>
    And <code>&lt;optgroup&gt;</code> tags will be converted into data objects using the following rules
  </p>

<pre class="prettyprint linenums">
{
  "text": "label attribute",
  "children": [ option data object, ... ],
  "elment": HTMLOptGroupElement
}
</pre>
</section>