Select2, when no option matches, "other" should appear

Question

With select2 dropdown, how do I get a default option to appear if no options match the user's typed input?

$("something").select2({
  formatNoMatches: function(term) {
    //return a search choice
  }
});

I haven't been able to find anything that really matches this desired functionality within the select2 documentation or Stack Overflow.

Edit I'm getting closer with this

$("something").select2({
  formatNoMatches: function(term) {
    return "<div class='select2-result-label'><span class='select2-match'></span>Other</div>"
  }
});

But this is pretty hacky off the bat, and also isn't clickable.

Answer 1

To complement on @vararis's answer:

Select2 attached to a <select> element does not allow for custom createSearchChoice nor query functions, hence we will need to manually add an option element (I'll add it as the last option of the element so we can easily .pop it out of the results set):

<select>
  ...
  <option value="0">Other</option>
</select>

Then pass a custom matcher function so that this "Other" option is always matched.

NOTE: Select2 3.4+ uses a different default matcher than the one currently shown in the documentation, this new one has a call to the stripDiacritics function so that a matches á for instance. Therefore I'll apply the default matcher that comes with the Select2 version included in the page to apply its default matching algorithm to any option that's not the "Other" option:

matcher: function(term, text) {
  return text==='Other' || $.fn.select2.defaults.matcher.apply(this, arguments);
},

Finally, we need to remove the "Other" option from the results set when there's any result besides the "Other" result (which is initially always in the results set):

sortResults: function(results) {
  if (results.length > 1) results.pop();
  return results;
}

Demo