Nativescript/Js. How can I change the appearance o

Question

How do I change the appearance of TabViewItem ()? I'm trying to set the radius of the border and the width of the border, as in the picture:

but it does not work:

var tabViewModule =  require("ui/tab-view");
    var tabEntry0 = new tabViewModule.TabViewItem();
        tabEntry0.borderRadius="30%";
        tabEntry0.borderWidth="30%";

Who know, how it doing.?