I'm developing an Angular WebApp and I would like to assign the value coming from an AJAX call to a variable. Actually, I tried many different solutions without good results.

let a = testFunction();

testFunction(){
let b;
$.ajax({...}).done(function(e) { b = e + 1  });
return b
}

console.log("The value of 'a' plus the value coming from the AJAX call is: " + a)

Let's suppose e=3, I would like to have this kind of result in the console:

The value of 'a' plus the value coming from the AJAX call is: 4

I know it could be quite confusing but I hope you can help me.