What is the TypeScript equivalent of “PropTypes.oneOf” (restrict a variable to subset of values)

Question

In React I can restrict a variable to subset of values, like

PropTypes.oneOf([\'Home\', \'About\']),

How do I do that in TypeScript?

Answer 1

Only one type among several one is a union type, and in your case a union of string literal.

You can convert an array of string literals into a union of string literals as follow:

If you do have a const array or string you can define a type:

const menuList = ["Home", "About"] as const;
type menuName = typeof menuList[number] // "Home" | "About"

If you do already have a type with the array just do:

type menuList = ["Home", "About"];
type menuItem = menuList[number] // "Home" | "About"