About one year ago, I used nacl.sign.keyPair in react-native framework, but it returned exception. So as it is mentioned in document I used this codes to resolve the issue:

nacl.setPRNG(function(x, n) {
  // ... copy n random bytes into x ...
});

But now, after about one year, I test to removing this lines of code (setPRNG) and test my application. it works without any exception.
Now my question is, In which platforms we need to redefine PRNG? and did you update anything that now it does not need to redefine PRNG in android platform?
Thanks in advance.