Validate whether or not string is enum value

I have a TypeScript enum

enum Items {
  One = 1,
  Two,
}

How can I know whether or not string s is a valid string representation of Items? For instance, 'One' is valid but '1' isn’t.

>Solution :

Enums get mapped to objects in JavaScript, so you can do the following:

enum Items {
  One = 1,
  Two,
}

function isEnumValue(s: string): s is keyof typeof Items {
    return s in Items;
}

There is a potential edge case here, because numeric enums also automatically get a reverse mapping. Passing a string representation of an enum value, would also make the above function return true:

console.log(isEnumValue('1')); // true

If needed, this can be addressed by additionally making sure that the key lookup returns a numeric value:

function isEnumValue(s: string): s is keyof typeof Items {
    return s in Items && typeof Items[s as any] === 'number';
}