Relevant answer from SO: Apparently Math.random() in V8 only works with 32 bit values (and didn't even correctly randomize all of those in the past). And with

Relevant answer from SO: Apparently Math.random() in V8 only works with 32 bit values (and didn't even correctly randomize all of those in the past). And with 32 bits, the probability of a collision reaches 50% around 2^16 = 65k values... Here is bug report: https://code.google.com/p/chromium/issues/detail?id=276886 https://code.google.com/p/chromium/issues/detail?id=276886