Javascript/jQuery - if the value of the input is

I want to make a working calculator. Now, i want to change between the operators.

Let's say I have + and -. Then, I have 2 numbers. The operator is between them.

If the value of the operator is +, it should calculate +. If the value of operator is -, it should calculate -.

I tried something like this but it doesnt work, help?

function Operator() {
            if ($('#realOperator').val == ('+');){
                    var a = parseInt($('input[name=a]').val());
                    var b = parseInt($('input[name=b]').val());
                    $('#total').val(a+b);
            }else
               $('#total').val(a-b);
            } 
        }

Information

#realOperator is the input with the operator

#total is the input with the result.

Thanks and sorry if even the syntax is wrong.. I'm new!