How to use the tns-core-modules/application.start function in tns-core-modules

import * as application from "tns-core-modules/application";

import * as trace from "tns-core-modules/trace";
trace.enable();
trace.setCategories(trace.categories.concat(
    trace.categories.Layout
//, trace.categories.NativeLifecycle
//, trace.categories.Navigation
//, trace.categories.ViewHierarchy
//, trace.categories.VisualTreeEvents
    ));

application.start({ moduleName: "styling/mainPage" });

import * as application from 'tns-core-modules/application';
application.start({ moduleName: 'main-page' });

import * as application from "tns-core-modules/application";

application.start({ moduleName: "main-page" });

import * as applicationModule from "tns-core-modules/application";
import * as frescoModule from "nativescript-fresco";

if (applicationModule.android) {
    applicationModule.on("launch", () => {
        frescoModule.initialize();
    });
}

applicationModule.start({ moduleName: "pages/main-page" });

import * as application from 'tns-core-modules/application';
application.start({ moduleName: "main-page" });

import * as application from 'tns-core-modules/application';
application.start({ moduleName: 'main-page' });

import * as application from 'tns-core-modules/application';
application.start({ moduleName: 'main-page' });

import * as application from 'tns-core-modules/application';

const tnsfx = require('nativescript-effects');

application.start({ moduleName: "main-page" });