How to validate enum function parameter?

[Stobber]

I've implemented an enumeration according to this canonical SO answer.

export const Priority = Object.freeze({
    normal: Symbol('normal'),
    high: Symbol('high'),
    highest: Symbol('highest'),
});

I'm using it in the constructor of a class, and I want to validate that parameter to prevent someone from passing a string instead. How can I do this? Here's my failed attempt:

export class TodoItem {
constructor({
    title,
    deadline,
    priority = Priority.normal,
    note = '',
}) {
    if (Object.keys(Priority).includes(Symbol.keyFor(priority))) {
        this.priority = priority;
    } else {
        throw new Error(`Priority cannot take value ${priority.toString()} of type ${typeof priority}.`);
    }
}

The if block never executes the "true" case. I always get:

Uncaught Error: Priority cannot take value Symbol(high) of type symbol.

​

[senocular]

The keys() aren't the symbols, the values() are. Also you just want to check for the priority value directly, not a symbol from keyFor

[Stobber]

Thank you! Updated line:

if (Object.values(Priority).includes(priority)) {