"query function not defined for Select2 undefined error"

This error message is too general. One of its other possible sources is that you're trying to call select2() method on already "select2ed" input.

In case you initialize an empty input do this:

$(".yourelement").select2({
 data: {
  id: "",
  text: ""
 }
});

Read the first comment below, it explains why and when you should use the code in my answer.

I also had this problem make sure that you don't initialize the select2 twice.

For me this issue boiled down to setting the correct data-ui-select2 attribute:

<input type="text" data-ui-select2="select2Options.projectManagers" placeholder="Project Manager" ng-model="selectedProjectManager">


$scope.projectManagers = { 
  data: []  //Must have data property 
}

$scope.selectedProjectManager = {};

If I take off the data property on $scope.projectManagers I get this error.

This issue boiled down to how I was building my select2 select box. In one javascript file I had...

$(function(){
  $(".select2").select2();
});

And in another js file an override...

$(function(){
    var employerStateSelector = 
                $("#registration_employer_state").select2("destroy");
    employerStateSelector.select2({
    placeholder: 'Select a State...'
    });
});

Moving the second override into a window load event resolved the issue.

$( window ).load(function() {
  var employerStateSelector = 
              $("#registration_employer_state").select2("destroy");
  employerStateSelector.select2({
    placeholder: 'Select a State...'
  });
});

This issue blossomed inside a Rails application

I also got the same error when using ajax with a textbox then i solve it by remove class select2 of textbox and setup select2 by id like:

$(function(){
  $("#input-select2").select2();
});

It seems that your selector returns an undefined element (Therefore undefined error is returned)

In case the element really exists, you are calling select2 on an input element without supplying anything to select2, where it should fetch the data from. Typically, one calls .select2({data: [{id:"firstid", text:"firsttext"}]).

Also got the same error when using ajax.

If you're using ajax to render forms with select2, the input_html class must be different from those NOT rendered using ajax. Not quite sure why it works this way though.

if (typeof(opts.query) !== "function") {
    throw "query function not defined for Select2 " + opts.element.attr("id");
}

This is thrown becase query does not exist in options. Internally there is a check maintained which requires either of the following for parameters

• ajax
• tags
• data
• query

So you just need to provide one of these 4 options to select2 and it should work as expected.

I got the same error. I have been using select2-3.5.2

This was my code which had error

    $('#carstatus-select').select2().val([1,2])

Below code fixed the issue.

    $('#carstatus-select').val([1,2]);

I have a complicated Web App and I couldn't figure out exactly why this error was being thrown. It was causing the JavaScript to abort when thrown.

In select2.js I changed:

        if (typeof(opts.query) !== "function") {
            throw "query function not defined for Select2 " + opts.element.attr("id");
        }

to:

        if (typeof(opts.query) !== "function") {
            console.error("query function not defined for Select2 " + opts.element.attr("id"));
        }

Now everything seems to work properly but it is still logging in error in case I want to try and figure out what exactly in my code is causing the error. But for now this is a good enough fix for me.

if you see this problem before like this "jquery.min.js:917 Uncaught ReferenceError: select2_dc80d1e9 is not defined. then finally i check all stuff and all results. So i come realizie maybe something wrong happyen in "/vendor/kartik-v/yii2-krajee-base/src/WidgetTrait.php" . As you can see in last plugin js. the $pos return 1. so i overwrite "$view->registerJs($js, $pos, $key);" to "$view->registerJs($js, View::POS_LOAD, $key);" OR "$view->registerJs($js, View::POS_END, $key);" problem resolved. hope you enjoy.