select2/docs/themes/site/js/data-fill-from.js

$(document).ready(function() {
  $("[data-fill-from]").each(function () {
    var $this = $(this);

    var codeContainer = $this.data("fill-from");
    var $container = $(codeContainer);

    var code = $.trim($container.html());

    $this.text(code);
    $this.addClass("prettyprint");
  });
});