How to skip an item and not include it when using mapping options in knockout js?

Question

I would like to only include and return items that have the selected property set to true when I am populating my arrays using the ko.mapping.fromJS utility.

I have written the following code but it is population the array with undefined if the items don't have the selected property.

    var mappingOptions = {
                create: function (options) {
                    if (options.data.Selected) {
                        var item = ko.mapping.fromJS(options.data);
                        return item;
                    }
                }
            };




   self.Medias = ko.mapping.fromJS(ko.toJS(data.Medias), mappingOptions);

the produced array should not have the undefined elements.

[Object, undefined, Object, undefined, Object, undefined, Object]

Answer 1

To be honest, you're better off filtering the JS data first:

var selectedMedia = ko.utils.arrayFilter(ko.toJS(data.Medias), function(item) {
        return item.Selected;
    });
self.Medias = ko.mapping.fromJS(ko.toJS(data.Medias), mappingOptions);