null or undefined?

[Cay Horstmann]

In Java, we use null for a reference to no object. JavaScript gives us two "bottom" values: null and undefined.

When I first learned JavaScript, I dutifully tried to make a distinction between "intentionally non-existent" (null) and "non-existent for some other reason" (undefined). But I always ended up in pointless metaphysical discussions and gave up. Now I always use undefined, except of course, when an API gives me null.

I am curious how others feel about this.

Cheers,

Cay

[Bear Bibeault]

Cay Horstmann wrote:Now I always use undefined, except of course, when an API gives me null.

I do the same -- undefined seems to capture the spirit of a, well, undefined value better than null; hair-splitting perhaps, philosophical perhaps, but a real distinction in my mind.

However, lots of code treats them interchangeably, and I cannot count the number of bugs I've had to deal with when code specifically checks for one or the other, but not both, in situations where a distinction is not made.

In this topic, I pointed out the fairly new nullish coalescing operator which helps a lot in this regard.