I create string arrays using const assertions and then use them to generate union types.
const elements = ["apple", "banana", "orange"] as const;
type elementsUnion = typeof elements[number]; // type elementsUnion = "apple" | "banana" | "orange"
Is there a way to streamline this process by creating a utility type that eliminates the need to repeatedly type typeof and [number]? I use this pattern frequently, so it would be beneficial to find a more concise approach.
It is impossible to eliminate the typeof in this scenario, as you cannot assign a value to a type. Instead, you need to specify the typeof that value when using it as a type within another type.
One approach could be defining a type like:
type ArrayMember<T extends readonly unknown[]> = T[number]
You can then utilize it as shown below:
const keys = ["foo", "bar", "moo"] as const;
type KeysUnion = ArrayMember<typeof keys> // "foo" | "bar" | "moo"
type MyKey = ArrayMember<string[]> // string
Although not significantly shorter, this method results in code that reads more smoothly compared to MyArrType[number].
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