Visual Studio NPM Task Runner fails, but running task outside of VS runs fine - node.js

Question

I'm working on bringing a ReactJS app over to a .NET setup. I'm trying to run an NPM script from the task runner (or anywhere within VS.) When I run my build command from the task runner, it fails due to an ES6 arrow function within one of my scripts. However, if I load up cmd.exe or powershell, navigate to the project and run it by hand, it runs perfectly.
Any idea why Visual Studio would be doing this?
The output looks something like this:
> cmd.exe /c npm run build --color=always
> ...cmd1
> ...cmd2
> mocha --reporter spec tools/testSetup.js "Scripts/app/**/*.test.js"
C:\Code\HAL\dev\Test\HALTest\HALReact\tools\testSetup.js:40
Object.keys(document.defaultView).forEach((property) => {
^
SyntaxError: Unexpected token >
at Module._compile (module.js:439:25)
at Object.Module._extensions..js (module.js:474:10)
at Module.load (module.js:356:32)
at Function.Module._load (module.js:312:12)
at Module.require (module.js:364:17)
at require (module.js:380:17)
at C:\Code\HAL\dev\Test\HALTest\HALReact\node_modules\mocha\lib\mocha.js:220:27
at Array.forEach (native)
at Mocha.loadFiles (C:\Code\HAL\dev\Test\HALTest\HALReact\node_modules\mocha\lib\mocha.js:217:14)
at Mocha.run (C:\Code\HAL\dev\Test\HALTest\HALReact\node_modules\mocha\lib\mocha.js:469:10)
at Object.<anonymous> (C:\Code\HAL\dev\Test\HALTest\HALReact\node_modules\mocha\bin\_mocha:404:18)
at Module._compile (module.js:456:26)
at Object.Module._extensions..js (module.js:474:10)
at Module.load (module.js:356:32)
at Function.Module._load (module.js:312:12)
at Function.Module.runMain (module.js:497:10)
at startup (node.js:119:16)
at node.js:906:3
The file that it errors on basically just sets up JSDOM:
process.env.NODE_ENV = 'test';
// Register babel so that it will transpile ES6 to ES5
// before our tests run.
require('babel-register')();
// Disable webpack-specific features for tests since
// Mocha doesn't know what to do with them.
require.extensions['.css'] = function () {return null;};
require.extensions['.png'] = function () {return null;};
require.extensions['.jpg'] = function () {return null;};
// Configure JSDOM and set global variables
// to simulate a browser environment for tests.
var jsdom = require('jsdom').jsdom;
var exposedProperties = ['window', 'navigator', 'document'];
global.document = jsdom('');
global.window = document.defaultView;
Object.keys(document.defaultView).forEach((property) => {
if (typeof global[property] === 'undefined') {
exposedProperties.push(property);
global[property] = document.defaultView[property];
}
});
global.navigator = {
userAgent: 'node.js'
};
documentRef = document; //eslint-disable-line no-undef
Again, I can run this from the CLI directly, and it will work. It has babel-register invoked. I'm just not sure why it wants to error here. If I swap out the arrow function with a regular function, I get other errors in my tests, so it's like the task runner is not able to find babel, or is losing some environmental setting.