Brunch using javascript-obfuscator package

I got this package javascript-obfuscator, installed it via npm install --save.

When I view source of the page it shows up as installed.

But when I try to use it as described in the documentation:

var obfuscationResult = JavaScriptObfuscator.obfuscate(source_code, options);```

it throws error saying:
```Uncaught ReferenceError: __dirname is not defined
    at pjson.js:7```

And that line 7 is this: `var root = path.resolve(__dirname, "..", "..");`

I am so confused of this npm and brunch thing ... have opened so many pages and tried various things but not able to resolve this. 

Any help will be appreciated.