According to this post on the official V8 Javascript blog, the pseudo-random number generator (PRNG) that V8 Javascript uses in Math.random() is horribly flawed and getting replaced with something … ...

Even with just 64 bits of state, you can generate a million random numbers per second, and still not repeat until the sun blows up. And it’s very easy to use a few thousand bits of state.

Over the years, multiple studies have found that Google Chrome’s V8 JavaScript engine was returning not-so-random numbers when you called the Math.random() function. Today that’s been fixed ...