Kata

When you're learning JavaScript, it can be easy to forget to "call" a function, to add those two little brackets () to the end of the function name, and the value of the function is coerced. The problem is, no error is thrown.

Now, there are cases when you'd want to use this functionality. But for this kata, let's assume any time a function is coerced, it means something unintended happen. Your job is to throw an error whenever such a coersion would occur.

function fn() { }
var a = fn;

a === fn; // true
fn < 1; // error
+fn; // error