Controller without $scope - angularjs

Question

I just come across some code where no $scope was there in the controller.
Here is the code
<div ng-app="myApp" ng-controller="ctrlCarLists as cars">
<button ng-click="cars.showCars()">
Cars
</button>
<button ng-click="alert(cars.data)">
Test
</button>
</div>
var app = angular.module('myApp', []);
app.controller("ctrlCarLists", function () {
this.data = 'hello';
this.showCars = function () {
alert("Ford, Toyata, Mercedes");
};
});
The above code is running, but this.data is not accessible...why? showCars() is accessible when the button is clicked. Why isn't this.data is not accessible?
What should be called when we declare any variable or function inside controller with the this keyword? Will it behave like a static property or function of a class?
jsfiddle link https://jsfiddle.net/tridip/z5wkzc0g/

Answer 1

ng-controller="ctrlCarLists as cars"
"cars" is referring to your controller, and "this" is refering to your controller as well.
ng-click="cars.showCars()"
When this function is triggered, it will refer to "showCars()" function in your controller.

Answer 2

As Yury Tarabanko has explained in his comment, alert function is not found, reason is:
https://docs.angularjs.org/guide/expression#context
Angular does not use JavaScript's eval() to evaluate expressions.
Instead Angular's $parse service processes these expressions.
Angular expressions do not have access to global variables like
window, document or location. This restriction is intentional. It
prevents accidental access to the global state – a common source of
subtle bugs.
Instead use services like $window and $location in functions called
from expressions. Such services provide mockable access to globals.
Source:
Why is ng-click not working?

Answer 3

ng-click requires an expression (see docs).
alert(cars.data)
is not an expression that angularJS can compile (it doesn't know what alert refers to) thus it should be replaced with
ng-click="cars.data()"
because cars.data() is an expression it can compile.
Fiddle
Or, alternatively
Fiddle
where we could have this:
this.alert = function (text) {
alert(text);
}