Why is the function called? JavaScript / Window

Question

I have the following code in my HTML file:

Answer 1

The function expression is followed by parenthesis:

 window.never = function() { ... }
 (...)

The line break after the function expression does not terminate the variable statement, so for the parser that's a function call:

function() { ... }(...)

In fact, you are using the very same technique here:

(function(d, s, id){
  // ...
}(document, 'script', 'streamrail-jssdk'))

That's a function expression followed by (...) and it calls the function.

Solution: Add a semicolon after the definition and you are good.

---

If I change the never function to be off the global scope ... Then it is not being called.

In that case the function definition is interpreted as function declaration, not expression. A function declaration is more like a statement and therefore cannot be part of a CallExpression. The following parenthesis are therefore interpreted as grouping operator (like you intended).

Answer 2

Place the semi-colon after the function declaration:

    window.never = function() {
             console.log('this function is never called');
    };

It's because of the (...) directly afterwards that triggers the function call.

    window.never = function() {
             console.log('this function is never called');
    }
    ( ... ) // <-- Triggers call of `window.never`