It depends on the implementation, e.g. Node has crypto.getRandomBytes()¹.
If you mean the standard browser implementation, Crypto.getRandomValues()² may be what you're looking for. Note that the browser implementation of this is only a recommendation, so YMMV:
> To guarantee enough performance, implementations are not using a truly random number generator, but they are using a pseudo-random number generator seeded with a value with enough entropy. The pseudo-random number generator algorithm (PRNG) may vary across user agents, but is suitable for cryptographic purposes. Implementations are required to use a seed with enough entropy, like a system-level entropy source.
> [...]
> There is no minimum degree of entropy mandated by the Web Cryptography specification. User agents are instead urged to provide the best entropy they can when generating random numbers, using a well-defined, efficient pseudorandom number generator built into the user agent itself, but seeded with values taken from an external source of pseudorandom numbers, such as a platform-specific random number function, the Unix /dev/urandom device, or other source of random or pseudorandom data.
... neither crypto.getRandomBytes() nor Crypto.getRandomValues() are SEEDABLE. There is no argument I could pass in that would produce the same random sequence for the same seed-value.
A reproducible random sequence would be useful in many situations I believe. I understand such a thing is not too difficult to program but it may be difficult to get verifiably good quality randomness out of your own implementation.
It's true that the standard is currently just a recommendation, but the implementation exists in every major browser already since, and including IE 11 https://caniuse.com/#search=getRandomValues
If you mean the standard browser implementation, Crypto.getRandomValues()² may be what you're looking for. Note that the browser implementation of this is only a recommendation, so YMMV:
> To guarantee enough performance, implementations are not using a truly random number generator, but they are using a pseudo-random number generator seeded with a value with enough entropy. The pseudo-random number generator algorithm (PRNG) may vary across user agents, but is suitable for cryptographic purposes. Implementations are required to use a seed with enough entropy, like a system-level entropy source.
> [...]
> There is no minimum degree of entropy mandated by the Web Cryptography specification. User agents are instead urged to provide the best entropy they can when generating random numbers, using a well-defined, efficient pseudorandom number generator built into the user agent itself, but seeded with values taken from an external source of pseudorandom numbers, such as a platform-specific random number function, the Unix /dev/urandom device, or other source of random or pseudorandom data.
¹ https://nodejs.org/api/crypto.html#crypto_crypto_randombytes...
² https://developer.mozilla.org/en-US/docs/Web/API/Crypto/getR...