How to reload jQuery multiselect in a drowdown list when the selection of another dropdown changes

Question

I have tried some of the solutions proposed in this forum but they did not work for so I think I am missing something somewhere.

I am using Patrick Springstubbe jQuery multiselect on two dropdown lists(ProductCategories and Products).

I want the list of products to change depending on what's selected in the ProductCategories multiselect.

The code I am using for that is as follows:-

  $("#ProductCategory").change( function () { $("#leftlist").empty(); $("#ProductCategory").children("option:selected").each(function () { ResetLeftList(($(this).val())); }); $('#leftlist').multiselect( 'reload' ); }); 

 function ResetLeftList(ProductCategoryID) { //Get list of food for categoryID $.ajax ({ url: "http://example.com/index.php?id=18", data: { PostProductCategoryID: ProductCategoryID }, method: "post", success: function(result) { var trimmedresult = result.substring(3, result.length - 4); var newOptions = trimmedresult.split(";"); for (i = 0; i < newOptions.length; i++) { var option = newOptions[i].split(","); $("#leftlist").append($("<option></option>").attr("value", option[0]).text(option[1])); } } }); } 

Problem:- The product multiselect don't update

Observation:- Using developer tool on the web browser I can see that the list of options in the product list is changing as expected. If I remove $("#leftlist").empty(); the product multilist updates based on the previously selected options from the category list. It appears that $('#leftlist').multiselect( 'reload' ) is firing before the option changes in the product list.

Answer 1

You are right "$('#leftlist').multiselect( 'reload' ) is firing before the option changes in the product list.".

jQuery.ajax performs an asynchronous HTTP (Ajax) request.

which means that code will continue executing after $.ajax() is called.

You can use the jqXHR Object returned by $.ajax() and place the reload code in a callback that will be executed when the request is finished.

Return the jqXHR Object:

function ResetLeftList(ProductCategoryID) {
    return $.ajax

Wait for all ajax to finish

 var requests = new Array();

 $("#ProductCategory").children("option:selected").each(function () {

     requests.push(ResetLeftList(($(this).val())));     

 });

 $.when.apply($, requests).done(function( x ) {
     $('#leftlist').multiselect( 'reload' );
 });