Optional Method Parameters

Let's say we have this problem:

"aRadius" is an optional parameter (if it is not passed, then it will be "undefined")
We want to always initialize the ivar "this.radius" to a number (default 0)

constructor(aRadius) {
	this.radius = aRadius;
}

Basic Assignment

In try 1 we simply assign the param to the ivar.

However, when the param is not passed (i.e. is "undefined") then that means "this.radius" will be set to an "undefined" value.

We need "radius" to a number, so this will not work.

constructor(aRadius) {
	this.radius = aRadius;
}

Conditional Assignment

Heer we use the handy ternary operator to handle the "undefined" case.

If "aRadius" is not equal to undefined, we use it, otherwise we use the default 0.

This works. This added logic "guards" against an "undefined" value.

constructor(aRadius) {
	this.radius = (aRadius !== undefined) ? aRadius : 0;
}