Select2 performance for large set of items

Question

I'm using select2 jquery plugin with twitter bootstrap. It's working fine for smaller number of items. But when the list is huge (more than 1500 items) it really slows down. It's slowest in IE.

Normal Dropdownlist works very fast with more than 1500 items. Are there any workarounds for this situation?

Answer 1

You can make this work good even in IE8 with paginating the suggestions,

Code:

// Function to shuffle the demo data
function shuffle(str) {
  return str
    .split('')
    .sort(function() {
      return 0.5 - Math.random();
  })
.join('');
}

// For demonstration purposes we first make
// a huge array of demo data (20 000 items)
// HEADS UP; for the _.map function i use underscore (actually lo-dash) here
function mockData() {
  return _.map(_.range(1, 20000), function(i) {
    return {
      id: i,
      text: shuffle('te ststr ing to shuffle') + ' ' + i,
    };
  });
}
(function() {
  // init select 2
  $('#test').select2({
    data: mockData(),
    placeholder: 'search',
    multiple: true,
    // query with pagination
    query: function(q) {
      var pageSize,
        results,
        that = this;
      pageSize = 20; // or whatever pagesize
      results = [];
      if (q.term && q.term !== '') {
        // HEADS UP; for the _.filter function i use underscore (actually lo-dash) here
        results = _.filter(that.data, function(e) {
          return e.text.toUpperCase().indexOf(q.term.toUpperCase()) >= 0;
        });
      } else if (q.term === '') {
        results = that.data;
      }
      q.callback({
        results: results.slice((q.page - 1) * pageSize, q.page * pageSize),
        more: results.length >= q.page * pageSize,
      });
    },
  });
})();

working example with 20000 items here: http://embed.plnkr.co/db8SXs/preview

plnkr embed does not support IE8 so try it out on IE8 with this link instead: http://run.plnkr.co/plunks/db8SXs/

Answer 2

I know it's an old question, but I wanted to share what worked for me. If you must pre-load the big list(depending on if you're starting from scratch or building on someone else's code, this may be easier), use the minimumInputLength as described here in the documentation. The huge list of options doesn't show until the user has typed a couple of characters. This greatly reduces the performance hit while rendering them when the Select2 dropdown is actually selected. Hope that helps!

Answer 3

Here's a working version for Select2 v4

Based on the answer here: and modified it to make searching work with lo-dash

$(function () {
    items = []
    for (var i = 0; i < 1000; i++) {
        items.push({ id: i, text : "item " + i})
    }

    pageSize = 50

    jQuery.fn.select2.amd.require(["select2/data/array", "select2/utils"],

    function (ArrayData, Utils) {
        function CustomData($element, options) {
            CustomData.__super__.constructor.call(this, $element, options);
        }
        Utils.Extend(CustomData, ArrayData);

        CustomData.prototype.query = function (params, callback) {

            var results = [];
            if (params.term && params.term !== '') {
              results = _.filter(items, function(e) {
                return e.text.toUpperCase().indexOf(params.term.toUpperCase()) >= 0;
              });
            } else {
              results = items;
            }

            if (!("page" in params)) {
                params.page = 1;
            }
            var data = {};
            data.results = results.slice((params.page - 1) * pageSize, params.page * pageSize);
            data.pagination = {};
            data.pagination.more = params.page * pageSize < results.length;
            callback(data);
        };

        $(document).ready(function () {
            $("select").select2({
                ajax: {},
                dataAdapter: CustomData
            });
        });
    })
});

JsFiddle: http://jsfiddle.net/nea053tw/

Edit: Fiddle changed.