Question

Question: What is the proper way to define a function in JavaScript that takes optional parameters?

For example:

function myFunc(optionVar1) {
    if(optionVar1 == undefined) {
        ...
    } else {
        ...
    }
}

myFunc('10');  // valid function call
myFunc();      // also a valid function call

Is it proper to use a ? mark like Ruby in the function declaration like so to denote optional parameters:

function myFunc(optionVar1?) {...}  //  <--- notice the ? mark

Answer 1

The first google response I discovered:

http://www.tipstrs.com/tip/354/Using-optional-parameters-in-Javascript-functions

I haven’t seen any instances where a question mark is used to alert a caller to an optional parameter. While it’s done in other languages, I don’t think it’s necessary in javascript.

In fact, it seems that you can’t use a question mark in the variable name. Only letters, numbers, $ and _.