select2/docs/pages/05.options/docs.md

title	taxonomy	process	never_cache_twig
Options	category docs	twig true	true

A traditional <select> box contains any number of <option> elements. Each of these is rendered as an option in the dropdown menu. Select2 preserves this behavior when initialized on a <select> element that contains <option> elements, converting them into its internal JSON representation:

{
  "id": "value attribute" || "option text",
  "text": "label attribute" || "option text",
  "element": HTMLOptionElement
}

<optgroup> elements will be converted into data objects using the following rules:

{
  "text": "label attribute",
  "children": [ option data object, ... ],
  "element": HTMLOptGroupElement
}

Options sourced from other data sources must conform to this this same internal representation. See "The Select2 data format" for details.

Dropdown option groups

In HTML, <option> elements can be grouped by wrapping them with in an <optgroup> element:

<select>
  <optgroup label="Group Name">
    <option>Nested option</option>
  </optgroup>
</select>

Select2 will automatically pick these up and render them appropriately in the dropdown.

Hierarchical options

Only a single level of nesting is allowed per the HTML specification. If you nest an <optgroup> within another <optgroup>, Select2 will not be able to detect the extra level of nesting and errors may be triggered as a result.

Furthermore, <optgroup> elements cannot be made selectable. This is a limitation of the HTML specification and is not a limitation that Select2 can overcome.

If you wish to create a true hierarchy of selectable options, use an <option> instead of an <optgroup> and change the style with CSS. Please note that this approach may be considered "less accessible" as it relies on CSS styling, rather than the semantic meaning of <optgroup>, to generate the effect.

Disabling options

Select2 will correctly handle disabled options, both with data coming from a standard select (when the disabled attribute is set) and from remote sources, where the object has disabled: true set.

First Second (disabled) Third

<select class="js-example-disabled-results">
  <option value="one">First</option>
  <option value="two" disabled="disabled">Second (disabled)</option>
  <option value="three">Third</option>
</select>