Check if a function is declared before using it in js

Issue: it may occurs that you have to call a function that is conditionally set. A frequent use case would be GDPR where you set your tracking script conditionally. You micht check the cookie for each event you track, but I think a better solution would be to track if he function is declared.

Solution:

There are two different options:

Option 1:

This option will still return an error in case the function to evaluate is not defined.

function isFunction(TrackingScript) {
   TrackingScript ('button-click','cart',10);
}

Option 2:

if (typeof( TrackingScript ) === typeof(Function)){
       TrackingScript ('button-click','cart',10); 
}