Value being exported instead of variable

Question

I've been trying to test out a module that simply exports a number, and a function that increments that number:

// counter.js
export var number = 0;
export function increment() {
  number++;
}

I'm then using this module as follows:

// index.js
import { number, increment } from './counter';

console.log(number);
increment();
console.log(number);

I'm using JSPM for the module loading, in case that's important. If I run this I get my expected output:

0
1

However, if I simply change counter.js to counter.ts and have TypeScript transpile this module, my output ends up being:

0
0

The transpiled counter.js looks like:

// counter.js
"use strict";
exports.number = 0;
function increment() {
    exports.number++;
}
exports.increment = increment;

Also, here is my tsconfig.json:

// tsconfig.json
{
    "compilerOptions": {
        "module": "commonjs",
        "target": "es5",
        "noImplicitAny": false,
        "sourceMap": false
    }
}

Is this a bug in how TypeScript is transpiling this module (and exporting a constant value for number, rather than the variable itself) or am I missing something here?

Answer 1

I have the exact same transpiled output and tsconfig.json settings, but I get the expected output:

0
1

The only difference I'm seeing is that you're using JSPM here, whereas I am not; I'm just running your code with Node.JS (v6.2.0, with TypeScript 3.8.9).

If it helps, the tsconfig.json documentation for valid --module options says amd, commonjs, system are some valid options.

I created a git repo of the working code.

https://github.com/TWebster/counter

I'm debugging with vscode in case it matters.

Answer 2

Updating my tsconfig.json with the following gave me my expected output:

{
    "compilerOptions": {
        "module": "system"
    }
}