Unities Javascript, declaring and using a non-generic function

You're not changing num, you're just using it in the method.

function should return x.

 function randomize (x : int) : int {
     return Random.Range(0, x);
 }
 
 function test () {
     var num : int = 10;
     num = randomize(num);
     print(num);
 
 }

I'm a C# programmer, I think this should work tho

okay in real JS this should print to the console "1"

Nope.

num is passed by value, which means that the x inside your randomize function is a copy of num. Changes to the copy won't affect the original.

If you'd like to learn more, search for a decent tutorial on "pass-by-value" versus "pass-by-reference".

To change the value of num, you could pass a value back:

 var num = 0;
 var randomize = function(x){
  
     return x+1;
  
  
 };
 num = randomize(num);
 print(num);

C# can do this by using the ref keyword in your method declaration. I assume JavaScript has some sort of equivalent functionality. However I would recommend using the return methods shown in the previous answers.

 int num = 0;
 
 private void randomise (ref int x){
     x = 1;
 }
 
 void testMethod (){
    print(num);
    // The console will show 0
    randomise(num);
    print(num);
    // The console will show 1
 }