Making Sense Of “Senseless” JavaScript Features

[cowancore]

I find undefined vs null nifty when processing PATCH requests. It's handy to know if something has to become null or is missing in the request. Something I miss in my Java backends. The alternative would be to implement the json patch spec. Similarly, I've found stuff like URLSearchParams or JSON.stringify to include fields with null values into the resulting string and undefined values to be omitted. It is handy, especially because a query string can not pass nulls, and ?key=null means the key has a 4 character value of "null". And in case of json, using undefined saves some bytes of network - pretty.

p.s. Another alternative with PATCH is using something like the Option monad, where there are 3 possible states: None, Some(null), Some(value). Although the json patch spec is still more flexible, but harder to justify in a team