NativeScript/apps/app/ui-tests-app/tab-view/tab-view-icon-local.ts

import { EventData } from "tns-core-modules/data/observable";
import { Button } from "tns-core-modules/ui/button";
import { TabView } from "tns-core-modules/ui/tab-view";

let iconModes = ["automatic", "alwaysOriginal", "alwaysTemplate", undefined];

export const onNavigate = updateButtons;

export function onChangeRenderingMode(args: EventData) {
    let tabView = (<Button>args.object).page.getViewById<TabView>("tab-view");
    tabView.iosIconRenderingMode = <"automatic" | "alwaysOriginal" | "alwaysTemplate">iconModes[(iconModes.indexOf(tabView.iosIconRenderingMode) + 1) % iconModes.length];
    updateButtons(args);
}

function updateButtons(args) {
    let button = (<Button>args.object);
    let tabView = button.page.getViewById<TabView>("tab-view");
    for (let i = 0, length = tabView.items.length; i < length; i++) {
        (<Button>tabView.items[i].view).text = "" + tabView.iosIconRenderingMode;
    }
}