undefined | Better HN

0 pointsMaster_Odin5y ago0 comments

Except in these cases, undefined still can make complete sense if you're willing to rephrase things (like sindresorhus is).

For your Node.firstChild example, one could say that if a node has no children, then it's firstChild is not defined as it doesn't exist, and so undefined makes sense. You can construct similar plausible arguments for other usages of null, though you cannot do the inverse.

0 comments

2 comments · 2 top-level

chrismorgan5y ago

Node.firstChild producing null is this conversation:

“Hey node, what’s your first child?” “I don’t have a first child.”

Node.firstChild producing undefined is this conversation:

“Hey node, what’s your first child?” “Huh? What’s a first child? I have no idea what you’re talking about.”

ZephyrBlu5y ago

Node.firstChild _is_ defined though, it's just empty. Hence null.

An undefined property would be one like Node.helloWorld, which doesn't not exist at all on the object.

j / k navigate · click thread line to collapse