How should I do an Enum comparison in typescript

user_390436 0
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I have a jhipster project and they just chanced the enum from this:

export enum DeclarationStatus {
  NEW = 'NEW',
  DRAFT = 'DRAFT',
  APPROVED_BY_FREELANCER = 'APPROVED_BY_FREELANCER',
  APPROVED_BY_CLIENT = 'APPROVED_BY_CLIENT',
  APPROVED = 'APPROVED'
}

to this:

export enum DeclarationStatus {
  NEW,
  DRAFT,
  APPROVED_BY_FREELANCER,
  APPROVED_BY_CLIENT,
  APPROVED
}

First I could do a comparison like this:

status === DeclarationStatus.APPROVED_BY_FREELANCER;

But now that does not work any more because the enum is actually a number. This does work how ever:

DeclarationStatus[''+status] === DeclarationStatus.APPROVED_BY_FREELANCER;

So my question is which is better. Or is there even a 3rd option?

I set this question to answered. The Jhipster community reverted the change to initialized. So then comparison is easy again.

Thanks to @vicpermir who made it happen.

jhipster typescript enums
1 Answers

The problem here is that the string enum is not initialized. As long as your enums are not defined as const you can make a very similar comparison as your old method.

status === DeclarationStatus[DeclarationStatus.APPROVED_BY_FREELANCER];

In other words, the following should work:

enum Initialized {
    A = 'A',
    B = 'B'
}

enum NotInitialized { // equivalent to
    A,                // A = 0,
    B                 // B = 1
}

status = 'A';

// String enum initialized
let test1 = (status === Initialized.A); // true

// String enum not initialized
let test2 = (status === NotInitialized.A); // false
let test3 = (status === NotInitialized[NotInitialized.A]); // true :)

In the official github repo for the JHipster Generator there is a recently merged pull request (PR#11218) that fixes this problem for React and forces the generator to always initialize string enums.

Remember that, as described in the JDL docs, you can also force this initialization:

enum DeclarationStatus {
   NEW (NEW),
   DRAFT (DRAFT)
}

More info about TypeScript Enums can be found here.

user_10312960
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