Kendo UI Image Upload Restriction for file type isn't working

Question

I want to restrict image upload to only jpg images using the kendo UI for ASP .NET MVC3. However, when I followed the example here ,even with my manipulation below, it keeps alerting "please upload jpg image files" even when I uploaded a jpg file! In fact, it makes me select all kinds of images. How can I change it so that I can only upload jpg images and if I upload png or other type of image files, it should alert, to only upload jpg images.

I put this into one of my views:

<script>
var onSelect = function (e) {
    $.each(e.files, function (index, value) {
        var ok = value.extension == ".JPG"
                 || value.extension == ".JPEG"
                 || value.extension == ".jpg"
                 || value.extension == ".jpeg";

        if (value.extension != ok) {
            e.preventDefault();
            alert("Please upload jpg image files");
        }
    });
};

// initialize and configure an Upload widget with a select event handler
$("#photos").kendoUpload({
    select: onSelect
});

Answer 1

You have a type-o:

value.expresion == ".jpg"

Should be:

value.expression == ".jpg"

Notice you are missing an 's'

EDIT

value.extension is a string which contains the extension. And ok is a boolean which determines if the correct extension was provided, so what you want to use to determine if to display the alert should be displayed needs to be udpated:

if (!ok) {
   e.preventDefault();
   alert("Please upload jpg image files");
}