Load selected values in dropdown on selecting value from another dropdown

Question

I have 2 dropdowns. When i select value from one dropdown it will load values in another dropdown depending upon what is selected.

Here is my html code

<select data-bind="options: filters, value: filter"></select>

<select data-bind="options: filteredItems, optionsText: 'name'"></select>

Here is my knockout code

var ViewModel = function(data) {
var self = this;
self.filters = ko.observableArray(data.filters);
self.filter = ko.observable('');
self.items = ko.observableArray(data.items);
self.filteredItems = ko.computed(function() {
    var filter = self.filter();
    if (!filter || filter == "None") {
        return self.items.slice(0, 6);
    } else {
        return self.items.slice(2);
    }
  });
};


  var initialData = {
     filters: ["None", "Old", "New", "Super"],
       items: [{ name: "Corvette", type: "Old"},
       { name: "Charger", type: "Old"},
       { name: "Prius", type: "New"},
       { name: "Magnum", type: "New"},
       { name: "McLaren", type: "Super"},
       { name: "Saleen", type: "Super"}]


   ko.applyBindings(new ViewModel(initialData));

When i select Type as None then it selects all Cars and if i select type other than None then it should only select "Charger" and "Magnum"

Here is the link to fiddle

Answer 1

First of all, if you want to return all items, just return self.items() , the slice is not needed. If you want to return items matching the filter, this should work:

self.filteredItems = ko.computed(function() {
    var myFilter = self.filter();
    if (!myFilter || myFilter == "None") {
        return self.items();
    } else {
        var tempArray = [];
        for(i=0; i<self.items().length; i++) {
            if(self.items()[i].type == myFilter) {
                tempArray.push(self.items()[i]);
            }
        }
        return tempArray;
    }
});

Check the working fiddle .

---

If you want to select only "Charger" and "Magnum" here it goes:

self.filteredItems = ko.computed(function() {
    var myFilter = self.filter();
    if (!myFilter || myFilter == "None") {
        return self.items();
    } else {
        return [ self.items()[1], self.items()[3] ];
    }
});