Typescript: Object.defineProperty(exports ...) is emitted even when exports is not defined

Created on 9 May 2017 · 9Comments · Source: microsoft/TypeScript

TypeScript Version: 2.3.2

Code

function fn(): void {}
export type MyType = number;

when compiled with a default tsconfig.json emits

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

Expected behavior:

It should not emit

Object.defineProperty(exports, "__esModule", { value: true });

if exports is not emitted in the compiled module.

Actual behavior:

Object.defineProperty(...) is emitted even if exports is not defined for the compiled module. When this code is loaded in a browser, it will throw an exception: Uncaught ReferenceError: exports is not defined.

If the MyType type declaration in the above code is not exported, then Object.defineProperty(...) is not emitted.

Working as Intended

Source

athasach

👍4

Most helpful comment

I am also facing same issue with the default values of jsconfig.json. what did you change to resolve this issue?

Bahetikr on 3 Jun 2017

👍5

All 9 comments

what is your target module system?

mhegazy on 9 May 2017

The default commonjs one for the tsconfig.json generated with tsc --init.

athasach on 9 May 2017

if exports is not emitted in the compiled module.

This isn't how it works. commonjs means there's an exports variable available. You can't run commonjs code directly in a browser.

RyanCavanaugh on 9 May 2017

Ah, I just figured out that I configured my project incorrectly. This whittled down example wasn't the issue as you indicated.

Curious though, why does only the presence of an exported type cause the Object.defineProperty(...) emit?

athasach on 9 May 2017

If it has an export, type or value, it's a module.

RyanCavanaugh on 9 May 2017

Okay, thank you.

athasach on 9 May 2017

I am also facing same issue with the default values of jsconfig.json. what did you change to resolve this issue?

Bahetikr on 3 Jun 2017

👍5

@Bahetikr If you want to use your transpiled TS in the browser, you could use a module loader like SystemJS.

Example

index.ts

export function fn(): void {
  console.log('fn() called');
}

fn();

index.html

<!DOCTYPE html>
<html>
<head>
  <script type="text/javascript"
    src="https://cdnjs.cloudflare.com/ajax/libs/systemjs/0.20.13/system.js">
  </script>
</head>
<body>
  <script type="text/javascript">
    // index.js is the transpiled index.ts
    SystemJS.import('/index.js');
  </script>
</body>
</html>

athasach on 3 Jun 2017