fix: Changed judgment of undefined to not use a function

[chimame]

Overview

Changed to not use isUndefined, which is deprecated in Node.js.

Reason for change

As written in the overview, it is deprecated in Node.js. I changed it because it is possible to determine without using it.

Also, this may be a personal opinion, but I use this library with Cloudflare Workers. There are two options to use Node.js API with Cloudflare Workers.

• node_compat
• nodejs_compat

I won't go into detail on how these two options are different, but the only way to make this library work is to use the former node_compat. Because to use the nodejs_compat option, you need to specify node: (node:util in this library) when using the Node.js API.

Initially, I used this library with the node_compat option, but started to migrate to using the nodejs_compat option. However, I noticed that this library cannot be built with the nodejs_compat option. Those are the isUndefined and util in this case.
I could have patched it to reference node:util, but when I looked at the Node.js documentation I noticed that it was deprecated, so I submitted a pull request to fix the library.

[chimame]

@maticzav ping

[cpvdeveloper]

Also facing this issue when trying to run on Node version 23

[tsongas]

Same issue.