JavaScript: Optional Callback?

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 t

Solution 1:

Ensure the callback is a function, and then invoke it.

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

    typeof callback == "function" && callback();
}

If you want more control over invoking it, use call(), apply(), bind() (whatever achieves your goal).

Solution 2:

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

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

    if (callback) {
        callback();
    }
}