Question

I have coded a function, that has 3 arguments, one of them is a callback function.
How do I make the callback an optional argument without having to code another function without the callback argument?

function myFunction(arg1, arg2, callback){
    // do something

    // callback() if it has been passed
}

Answer 1

Simple, just check if callback is defined before you call it.

function myFunction(arg1, arg2, callback){
    // do something

    if (callback) {
        callback();
    }
}