Demo what I would expect

class Demo:
    var = 10

    def add(self, addNum):
        print(f'adding {addNum} and {self.var} ')
        return self.var + addNum

class Demo2:
    def __init__(self, objref):
        var = 2
        self.objref = objref

    def increment(self):
        self.objref.var += 1

    def define_Callback(self, callback):
        self.callback = callback

if __name__ == "__main__":
    # this is the same as js / etc / most langs
    obj = Demo()
    obj2 = Demo2(obj)
    obj2.increment()

    obj2.define_Callback(obj.add)
    print('obj.var is', obj.var)
    var = obj2.callback(5)
    print('var + 5 = ', var)

outputs:

--- output ---
obj.var is 11
adding 5 and 11 
var + 5 =  16

meanwhile in crazy town...

class Demo {
    var = 10;

    add(num2Add) {
        console.log(`adding ${num2Add} to ${this.var}`);
        this.var += num2Add;
        return this.var;
    }
}

class Demo2 {
    constructor(objref) {
        this.objref = objref;
        this.var = 5;
        this.callback = null;
    }

    increment() {
        this.objref.var++;
    }

    defineCallback(callback) {
        this.callback = callback;
    }
}

var obj = new Demo();
var obj2 = new Demo2(obj);
obj2.increment();

obj2.defineCallback(obj.add);
console.log('obj.var is ' + obj.var);
var newvar = obj2.callback(5);
console.log(`var (${obj.var}) + 5 isn't ${newvar}`); // 16

Crazy town output

--- output ---
obj.var is 11
adding 5 to 5
var (11) + 5 isn't 10

Realize it is what it is, but this is mostly what screws me up