For instance:
type Y = 'c' | 'd';
const yVals = ??? Y; // ['c', 'd']
Alternatively, you can derive a union type from an array of all possible values.
The objective is to ensure each potential value is included only once.
For instance:
type Y = 'c' | 'd';
const yVals = ??? Y; // ['c', 'd']
Alternatively, you can derive a union type from an array of all possible values.
The objective is to ensure each potential value is included only once.
It's impossible to switch from a data type to an actual value directly. However, you can reverse the process by starting with a value and then determining its data type. The issue arises when the array containing values like ['a', 'b'] is automatically assigned the type string[], causing the elimination of string literal type unions.
The workaround involves employing a function to prompt the compiler to recognize string literal types for specific values:
function stringTuple<T extends [string] | string[]>(...data: T): T {
return data;
}
let xValues = stringTuple('a', 'b') // recognized as ["a", "b"]
type x = typeof xValues[number] // 'a' | 'b'
For a different approach to the stringTuple function mentioned in @Titian's response, starting from TypeScript 3.4 you have the option to utilize a const assertion:
const xValues = ['a', 'b'] as const; // type: readonly ["a", "b"]
type X = typeof xValues[number]; // type: "a" | "b"
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