Should we drop null?

[mxdvl]

Whilst there is a small semantic difference between undefined and null, we tend to use either somewhat interchangeably in our codebases. When using Typescript, there are a lot of shorthands for undefined values that don’t exist for null, such as the question mark ? against a key, or declaring a let without using a union type. Also, typeof null === "object". See Sindre Sorhus’s idea for other reasons.

Following a chat discussion, the value of a change needs to be proven. So I’ll try to find concrete examples where we would gain from choosing to drop null from our codebase, maybe using an ESLint plugin.

One key thing to keep in mind is that we you cannot use undefined in JSON.

WIP List, while I get to a minimum of 5

1. getCookie returns null, even if the cookie isn’t present.
2. in coreWebVitals we coerce from undefined to null, which leads to strange types. This may be because JSON does not support undefined values, but our backend processing will lead to the same data being in BigQuery.