How to find a function in code?

Question

JavaScript

Hello.
I need to find one function in javascript code, i don't know which version of angular is used.
I don't learn angular, I just need to understand how the code works,

app.controller("bla_bla_bla", ["$filter", "$scope", "$location", "$timeout", "$route", "urlService", "isValidDateFilter", function($filter, $scope, $location, $timeout, $route, urlService, isValidDate) {

...
...

if(isValidDate(row["sdu"])){ // <-- фот эту функцию хочу найти isValidDate()
 ...
}else{
 ...
}


});

As you can see, I gave only a part of the code where there is the isValidDate () function that interests me, I need to see how everything is arranged inside it, what kind of logic is there.
As you can see from the code, several arguments $filter, $scope, $location, $timeout, $route, urlService, isValidDate are passed to the controller, among which there seems to be the function that I'm looking for ...
The fact is that nowhere in the code (there are a couple of tens of thousands of lines) there is no more mention of "isValidDate" , in the source code of the page on the site too, I went through all the js scripts from that site and there is no "isValidDate" anywhere. And I don't understand angular, I prefer vanilla, so the question is probably stupid.