Math.random() vs Crypto.getRandomValue()

Math.random() is implemented using a pseudo-random number generator (PRNG) - the random number is derived from an internal state, which is altered by a fixed algorithm for every new random number. The sequence of random numbers is deterministic.

Crypto.getRandomValues() use a pseudo-random number generator seeded with a value with enough entropy. Implementations do not use a truly random number generator to guarantee enough performance but the output is suitable for cryptographic purposes.

crypto.getRandomValues(new Uint8Array(10))
// Uint8Array(10) [85, 215, 117, 156, 114, 11, 222, 34, 65, 119]