Error on converting enum from Typescript to JavaScript

Question

I have an enum in Typescript let's say

export const enum CarType {
    SED = "Sedan"
}

The JavaScript code after build :

"use strict";
Object.defineProperty(exports,"_esModule, { value: true })

:

So basically the js code doesn't have the logic, instead only the .d.ts file has the same. When I build it using tsc command and export the JavaScript code to a react app, while accessing this enum like: CarType.SED, it is giving an error like - Cannot read property SED of undefined

What could be the reason for the same. I understood that the typescript has a declaration file(of extension .ts). How can I use this in a purely JS project?

You should probably post your javascript code as well

Florian F.
– Florian F.

2018-11-07 20:18:25 +00:00
Commented Nov 7, 2018 at 20:18 — Florian F.
– Florian F., Commented Nov 7, 2018 at 20:18
@Florian, added the JS code as well

Amal
– Amal

2018-11-07 20:59:55 +00:00
Commented Nov 7, 2018 at 20:59 — Amal
– Amal, Commented Nov 7, 2018 at 20:59

Felix Kling · Accepted Answer · 2018-11-07 21:06:03Z

1

From the documenation:

Const enums can only use constant enum expressions and unlike regular enums they are completely removed during compilation. Const enum members are inlined at use sites. This is possible since const enums cannot have computed members.

Removing the const keyword should work. The inlining can only work if you use the enum in another TypeScript file.

answered Nov 7, 2018 at 21:06

Felix Kling

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Comments

Allenaz · Accepted Answer · 2020-01-06 10:53:57Z

1

You can set the compiler option (TSC options) "preserveConstEnums" as true:

tsconfig.json:

{
  "compilerOptions": {
    "preserveConstEnums": true,
    ...
  },
  ...
}

Or command line:

tsc --preserveConstEnums true path/to/some_file.ts

constant enum spec

answered Jan 6, 2020 at 10:53

Allenaz

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