Is `Union` of strings and `string` achievable?

January 25, 2022

Is they’re a way to have an union of string type that accepts some specific strings AND string ?

type AcceptsWithString =
 | 'optionA'
 | 'optionB'
 | 'optionC'
 | string

playground

The aim here is to have a type that offer auto completion for inputs (list can be long and we can make errors easily in some cases) AND also any string ?

>Solution :

I do know of a trick which can be used to confuse the IDE into still showing individual strings as autocomplete suggestions. There’s no guarantee that this will work for ever, but it works as of the current versions of typescript:

type AcceptsWithString =
 | 'optionA'
 | 'optionB'
 | 'optionC'
 | string & {}

string & {} doesn’t have any properties that string doesn’t already have, so you can still assign any string to this. But it confuses the editor enough that it can’t be sure that "optionA" and the others are redundant, so it keeps showing them.