I’m trying to define a type for an array where the value must contain specific values in a specific order at the beginning of the array.
type SpecificArray = ('hello'|'goodbye'|string)[]
// Currently
const myArray: SpecificArray = [] // okay
const myArray: SpecificArray = [''] // okay
const myArray: SpecificArray = ['something'] // okay
const myArray: SpecificArray = ['hello'] // okay
const myArray: SpecificArray = ['hello', 'goodbye'] // okay
const myArray: SpecificArray = ['hello', 'goodbye', 'something'] // okay
// Desired
const myArray: SpecificArray = [] // fail
const myArray: SpecificArray = [''] // fail
const myArray: SpecificArray = ['something'] // fail
const myArray: SpecificArray = ['hello'] // fail
const myArray: SpecificArray = ['hello', 'goodbye'] // okay
const myArray: SpecificArray = ['hello', 'goodbye', 'something'] // okay
I’ve tried various options, but none have had the desired effect…
type SpecificArray = ('hello'|'goodbye'|string)[]
/* ---- */
type SpecificArray = ['hello'|'goodbye'|string]
/* ---- */
import type { LiteralUnion } from 'type-fest'
type SpecificArray = LiteralUnion<'hello'|'goodbye', string>[]
Thank you in advance!
>Solution :
If the order is fixed in your array, then this works:
type SpecificArray = ["hello", "goodbye", ...string[]];