How to tell if a popup will get blocked

I appreciate how browsers work when deciding whether a window.open() was triggered by a click, as in, it's only allowed when it came from a real element click event.

I want to write the same logic myself, how do I do that?

Say I have any JS function, called potentially anywhere and everywhere from the rest of my application, sometimes with a click event handler at the start of the callstack and some times not. How can I know this inside my method, without explicitly passing information about the start of the stack (click vs not) all the way around my application?

function iNeedToKnowIfStackFrame0WasAClickEventListener() {
  var wasAClick = ???;
  if(wasAClick)
    window.open(...);
  else
    something.else();
}

You can get the event information using this.event.type. You can either pass the event into the function like so:

function iNeedToKnowIfStackFrame0WasAClickEventListener(event) {   
    var wasAClick = event.type == "click";    
    if(wasAClick)
        window.open(...);   
    else
        something.else(); 
}

or you can get the event off this

function iNeedToKnowIfStackFrame0WasAClickEventListener() {   
    var wasAClick = this.event.type == "click";    
    if(wasAClick)
        window.open(...);   
    else
        something.else(); 
}