rng-browser.js (1312B)
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 6 // getRandomValues needs to be invoked in a context where "this" is a Crypto 7 // implementation. Also, find the complete implementation of crypto on IE11. 8 var getRandomValues = (typeof(crypto) != 'undefined' && crypto.getRandomValues && crypto.getRandomValues.bind(crypto)) || 9 (typeof(msCrypto) != 'undefined' && typeof window.msCrypto.getRandomValues == 'function' && msCrypto.getRandomValues.bind(msCrypto)); 10 11 if (getRandomValues) { 12 // WHATWG crypto RNG - http://wiki.whatwg.org/wiki/Crypto 13 var rnds8 = new Uint8Array(16); // eslint-disable-line no-undef 14 15 module.exports = function whatwgRNG() { 16 getRandomValues(rnds8); 17 return rnds8; 18 }; 19 } else { 20 // Math.random()-based (RNG) 21 // 22 // If all else fails, use Math.random(). It's fast, but is of unspecified 23 // quality. 24 var rnds = new Array(16); 25 26 module.exports = function mathRNG() { 27 for (var i = 0, r; i < 16; i++) { 28 if ((i & 0x03) === 0) r = Math.random() * 0x100000000; 29 rnds[i] = r >>> ((i & 0x03) << 3) & 0xff; 30 } 31 32 return rnds; 33 }; 34 }