uuid.js not using crypto.getRandomValues when built with browserify

I ran into a problem using the node-uuid library. I was building with browserify, and I found that despite running in a modern browser that supported the crypto API, it wasn't actually using the crypto.getRandomValues method to generate randomness.

Short answer:

We found that the problem was caused by an incorrect configuration of browserify-shim. In package.json, add the following line:

  "browserify-shim": {
    "node-uuid": "uuid"
  }

Longer answer:

In uuid.js, it has the following initialization:

if (!_rng && _global.crypto && crypto.getRandomValues) {
    // WHATWG crypto-based RNG - http://wiki.whatwg.org/wiki/Crypto
    //
    // Moderately fast, high quality
    var _rnds8 = new Uint8Array(16);
    _rng = function whatwgRNG() {
      crypto.getRandomValues(_rnds8);
      return _rnds8;
    };
  }

The value of _global was an anonymous object, and the value of _global.crypto was undefined. After we added the above configuration, the value of _global was window and _global.crypto had the expected value.

The reason is, that when you configure browserify-shim, we are telling it that the node-uuid library will export the variable uuid into the calling environment. In a browser, the calling environment will be window, so when it runs the initialization for node-uuid, it sets things up so that the calling environment is the window.

If you don't configure it as such, then browserify-shim thinks node-uuid isn't returning any values, so the calling environment is set up as an anonymous object.