TypeScript

832 readers

1 users here now

founded 1 year ago

MODERATORS

snowe

[email protected]

Ategon

Writing exhaustive switch statements in TypeScript (arendjr.nl)

submitted 8 months ago by arendjr to c/typescript

5 comments fedilink hide all child comments

Today I'm sharing a little trick that I like to use to make switch statements cleaner and more type-safe. Happy to hear other ideas!

you are viewing a single comment's thread
view the rest of the comments

[–] towerful 3 points 8 months ago (2 children)

Just have default throw an error? Then, if you add a value to the string union (hopefully) your tests will highlight it isnt handled.

Equally, for such a simple switch, surely a map is better?
But i rarely find myself using switches.
I find ifs with early returns cleaner. Allows for variable creation during execution (which my tslint complains about)

[–] arendjr 5 points 8 months ago

Generally, I would recommend against throwing in the default case, since it will actually reduce your type safety (exceptions bypass all your other types). But I learned that with another clever trick this can be avoided, giving both runtime and compile time safety: https://exploringjs.com/tackling-ts/ch_enums.html#exhaustiveness-checks

[–] [email protected] 2 points 8 months ago

I really appreciate compile errors in this scenario. In Rust the compiler will freak out when there are missing enum variants in a match. Tests are great, but compiler errors don't rely on exhaustive and properly written tests.