Select2 multiple initial pre-selected options

Question

I'm trying to get select2 working with multiple pre-selected options. I'm using it to let users choose several options then have them saved to then be able to come back and edit them. however I can't get the select2 initSelection to work correctly to populate the existing options the user has already chosen. here is the code i have tried using with alerts to show when something has fired however the alert("done"); has never fired yet and the alert($(element).val(0) fires twice. once with the value in the input and then again with a blank.

<input type="text" id="Commissioners" name="Commissioners" value="test" />

$("#Commissioners").select2({
                placeholder: 'Select Commissioners',
                minimumInputLength: 2,
                allowClear: true,
                multiple: true,
                width: 'resolve',
                ajax: {
                    url: "/Commissioner/CommissionerAutoComplete/",
                    dataType: 'json',
                    data: function (term, page) {
                        return {
                            search: term // search term
                        };
                    },
                    results: function (data) {
                        return { results: data };
                    }
                },
                initSelection: function (element, callback) {
                    // the input tag has a value attribute preloaded that points to a preselected make's id
                    // this function resolves that id attribute to an object that select2 can render
                    // using its formatResult renderer - that way the make text is shown preselected
                    alert($(element).val());
                    $.ajax({
                        url: "/UserProfile/LoadServiceTypeAndCommissioners",
                        type: "GET",
                        dataType: "json",
                        data: { UserId: '@Model.UserID', serviceTypeId: id}                            
                    }).done(function (data) {
                        alert("done");
                        callback(data.results);
                    });

                },
                formatResult: s2FormatResult,
                formatSelection: s2FormatSelection
            }).select2('val', []);



I figured out that the second alert fires for the .select2('val', []); at the end. however removing this causes the placeholder to not work and adding in a value here like ["1"] does not result in a selected item

Answer 1

it turns out it was a combination of things that caused it to not work. I was not returning the code from the ajax call as a json object but that alone didn't fix it. I had to add success and error options to the ajax call with the call back in the success. weirdly i still needed to keep the .done with its callback as well.

$("#Commissioners").select2({
                placeholder: 'Select Commissioners',
                minimumInputLength: 2,
                allowClear: true,
                multiple: true,
                width: 'resolve',
                ajax: {
                    url: "/Commissioner/CommissionerAutoComplete/",
                    dataType: 'json',
                    data: function (term, page) {
                        return {
                            search: term // search term
                        };
                    },
                    results: function (data) {
                        return { results: data };
                    }
                },
                initSelection: function (element, callback) {
                    // the input tag has a value attribute preloaded that points to a preselected make's id
                    // this function resolves that id attribute to an object that select2 can render
                    // using its formatResult renderer - that way the make text is shown preselected
                    //alert($(element).val());
                    $.ajax({
                        url: "/UserProfile/LoadServiceTypeAndCommissioners",
                        type: "GET",
                        dataType: "json",
                        data: { UserId: '@Model.UserID', serviceTypeId: id },
                        success: function (data) {                                
                            callback(data);
                        },
                        error: function (data) {

                        }
                    }).done(function (data) {                            
                        callback(data.results);
                    });

                },
                formatResult: s2FormatResult,
                formatSelection: s2FormatSelection
            }).select2('val', ["1"]);

Answer 2

Here's the problem I see here: $.ajax call takes time to receive data, and select2 constructor doesn't wait for initSelection setting.

Try to move ajax call away from select2 initialization to a function and call it right after select2 initialization