Checks if a value exists in an array in a type safe manner

is.ts

/**
 * Checks if a value exists in an array in a type safe manner
 * @param value Value to check
 * @param arr An array of possible matches
 * @returns A boolean indicating if a passed value is one of the items in the array
 */
export function is<V extends string | number, Arr extends readonly [V, ...V[]]>(
	value: unknown,
	arr: Arr,
): value is Arr[number] {
	return arr.includes(value as V);
}

// Playground: https://www.typescriptlang.org/play?#code/KYDwDg9gTgLgBAMwK4DsDGMCWEV0wZwB4A1OUGYFAE3znxikxQHM4AfOFJAWwCNgoAGjgBBKFDIgK1WlGABDKjgA2ATzgBtYsIB0e4hoC6hgHwAKALAAoAJAA3ecqTAAXHFQBrFBADuKQdY28uJuYkLWAJRuDk7AeLRhGlx8AoZwAN6BcjBIULjBUDpMaE5UwPhmMc5w8rTEEQDc1gC+1tYA9O1wAMK18DAQcAAGtXQMTMxDcANkULVxAOQAFsDKgz7QylQL06pgwDrWaDj0cFVxALxwy6vrm9s1tPSMLE1W1pgIcGYElY7Owg0NzWcA2UC2C2EwJBYIhhgiEQygU6Z3+cQIdHkCFW6hge2AVDgKzkLTIynwcUythR53inGAmBgxJaQA