main-page.js

/*
In NativeScript, a file with the same name as an XML file is known as
a code-behind file. The code-behind is a great place to place your view
logic, and to set up your page’s data binding.
*/

/*
NativeScript adheres to the CommonJS specification for dealing with
JavaScript modules. The CommonJS require() function is how you import
JavaScript modules defined in other files.
*/ 
var createViewModel = require("./main-view-model").createViewModel;
var buttonModule = require("tns-core-modules/ui/button");

function onNavigatingTo(args) {
    /*
    This gets a reference this page’s <Page> UI component. You can
    view the API reference of the Page to see what’s available at
    https://docs.nativescript.org/api-reference/classes/_ui_page_.page.html
    */
    var page = args.object;

    /*
    A page’s bindingContext is an object that should be used to perform
    data binding between XML markup and JavaScript code. Properties
    on the bindingContext can be accessed using the {{ }} syntax in XML.
    In this example, the {{ message }} and {{ onTap }} bindings are resolved
    against the object returned by createViewModel().

    You can learn more about data binding in NativeScript at
    https://docs.nativescript.org/core-concepts/data-binding.
    */
    page.bindingContext = createViewModel();
    console.log("### TEST START ###");
    console.time("Time");

    var undef;
    var num = -1;
    var str = "text";
    var obj = { name: "John", age: 34 };
    var button = new buttonModule.Button();

    var one_hundred_symbols_string="1234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890"
    var very_long_string = "";

    for (i = 0; i < 30; i++) {
        very_long_string = very_long_string + one_hundred_symbols_string;
    }

    console.log(very_long_string);
    console.log(true);
    console.log(false);
    console.log(null);
    console.log(undef);

    console.log(num);
    console.log(str);
    console.log(obj);

    console.log(`number: ${num}`);
    console.log(`string: ${str}`);
    console.log(`${str} ${num}`);
    console.info("info");
    console.warn("warn");
    console.error("error");

    console.assert(false, `false == true`);
    console.assert(true, "1 equals 1");

    console.assert("", "empty string evaluates to 'false'");

    console.trace("console.trace() called");
    console.log(`${button}`);

    console.log(num, str, obj);
    console.log([1, 5, 12.5, obj, str, 42]);

    console.trace();

    console.timeEnd("Time");
    console.log("### TEST END ###");
}

/*
Exporting a function in a NativeScript code-behind file makes it accessible
to the file’s corresponding XML file. In this case, exporting the onNavigatingTo
function here makes the navigatingTo="onNavigatingTo" binding in this page’s XML
file work.
*/
exports.onNavigatingTo = onNavigatingTo;