How did non-unique values ​​get into Set?

Question

typescript

I have an array of groups that a CRM user is a member of (array of identifiers)

And of course, they must all be unique, because a user cannot be in the same group 2 times at the same time, but JS doesn’t think so...

To list ID was unique, I use Set, it works in all parts of my code except for this one.

To uniqueize an array, you just need to call the Set constructor and pass this array there, in the screenshot I just output the result to the console.

There are no random imports like import Set from 'not-working-set', this is the most native Set, the type of this.groups is string[].

Help...

Answer 1

There is a difference between a literal string "habr", a primitive, String("habr")and an object new String("habr"). In the latter case typeof === "object", miracles happen:

const x = new String("habr");
const y = new String("habr");
x === y // false

Accordingly, it Set()will be able to store instances of objects, which only when reduced to a primitive will give the same strings, and so the essence is different instances. Maybe this is your case?