Question

I have a script I am requiring from a Node.js script, which I want to keep JavaScript engine independent.

For example, I want to do exports.x = y; only if it’s running under Node.js. How can I perform this test?

---

When posting this question, I didn’t know the Node.js modules feature is based on CommonJS.

For the specific example I gave, a more accurate question would’ve been:

How can a script tell whether it has been required as a CommonJS module?

Answer 1

By looking for CommonJS support, this is how the Underscore.js library does it:

Edit: to your updated question:

(function () {

    // Establish the root object, `window` in the browser, or `global` on the server.
    var root = this; 

    // Create a reference to this
    var _ = new Object();

    var isNode = false;

    // Export the Underscore object for **CommonJS**, with backwards-compatibility
    // for the old `require()` API. If we're not in CommonJS, add `_` to the
    // global object.
    if (typeof module !== 'undefined' && module.exports) {
            module.exports = _;
            root._ = _;
            isNode = true;
    } else {
            root._ = _;
    }
})();

Example here retains the Module pattern.