rng-browser.js 1.3 KB

12345678910111213141516171819202122232425262728293031323334
  1. // Unique ID creation requires a high quality random # generator. In the
  2. // browser this is a little complicated due to unknown quality of Math.random()
  3. // and inconsistent support for the `crypto` API. We do the best we can via
  4. // feature-detection
  5. // getRandomValues needs to be invoked in a context where "this" is a Crypto
  6. // implementation. Also, find the complete implementation of crypto on IE11.
  7. var getRandomValues = (typeof(crypto) != 'undefined' && crypto.getRandomValues && crypto.getRandomValues.bind(crypto)) ||
  8. (typeof(msCrypto) != 'undefined' && typeof window.msCrypto.getRandomValues == 'function' && msCrypto.getRandomValues.bind(msCrypto));
  9. if (getRandomValues) {
  10. // WHATWG crypto RNG - http://wiki.whatwg.org/wiki/Crypto
  11. var rnds8 = new Uint8Array(16); // eslint-disable-line no-undef
  12. module.exports = function whatwgRNG() {
  13. getRandomValues(rnds8);
  14. return rnds8;
  15. };
  16. } else {
  17. // Math.random()-based (RNG)
  18. //
  19. // If all else fails, use Math.random(). It's fast, but is of unspecified
  20. // quality.
  21. var rnds = new Array(16);
  22. module.exports = function mathRNG() {
  23. for (var i = 0, r; i < 16; i++) {
  24. if ((i & 0x03) === 0) r = Math.random() * 0x100000000;
  25. rnds[i] = r >>> ((i & 0x03) << 3) & 0xff;
  26. }
  27. return rnds;
  28. };
  29. }