cruk-pattern-library/assets/js/cruk-base/plugin-alphabetic-list.js

CRUK Pattern library.

jQuery(document).ready(function ($) {
  'use strict';

  $(document).on('click', '.cr-filter-input .btn-reset', function () {
    $("input.cr-filter-input__input").val('');
    $('.cr-index__list-item, .cr-index__category').show();
  });

  $(document).on('keyup', 'input.cr-filter-input__input', function () {
    var that = this,
      listId = $(this).data('cr-filter-list'),
      $allListElements = (listId) ? $('#'+listId) : $('.cr-index');
    $allListElements = $allListElements.find('.cr-index__list-item, .cr-index__category');
    var $matchingListElements = $allListElements.filter(
      function (i, li) {
        var listItemText = $(li).text().toUpperCase(), searchText = that.value.toUpperCase();
        return ~listItemText.indexOf(searchText);
      }
    );

    $allListElements.hide();
    $matchingListElements.show();
  });

  $(document).on('submit', 'form.cr-filter-form', function(e){
    e.preventDefault();
  });
});