randomWithSeed.js - use rnd() after rnd = createRandomWithSeed( seed [0+] = Date.now() ) - Math.random is less than 2x faster than this 'good enough' SEED-able version

randomWithSeed.js

// randomWithSeed.js - use rnd() after rnd = createRandomWithSeed( seed [0+] = Date.now() ) - Math.random is less than 2x faster than this 'good enough' SEED-able version

let createRandomWithSeed = seed => {
  seed = Math.abs(isNaN(seed) ? Date.now() : seed);
  return () => {
    seed = (seed * 9301 + 49297) % 233280;
    return seed / 233280;
  };
};
// R=s=>(s=Math.abs(isNaN(s)?Date.now():s),_=>(s=(9301*s+49297)%233280,s/233280));
// ^ 79 chars minified (FASTER than the "Modulus 4294967296" combo, but it visibly repeats earlier)

let createRandomWithSeed_SLOWER_BUT_LONGER_PERIOD = seed => {
  seed = Math.abs(isNaN(seed) ? Date.now() : seed);
  return () => {
    seed = (seed * 1664525 + 1013904223) % 0x100000000; // 0x100000000 (2 ^ 32) = 4294967296
    return seed / 0x100000000;
  };
};
// R=s=>(s=Math.abs(isNaN(s)?Date.now():s),_=>(s=(1664525*s+1013904223)%4294967296,s/4294967296));
// ^ 95 chars minified (SLOWER than the "Modulus 233280" combo, but this does not visibly repeat as early)



// based on http://indiegamr.com/generate-repeatable-random-numbers-in-js/ , e.g. http://demos.indiegamr.com/jumpy/seededRandomLevel/?seed=1.57251
// ( found via https://github.com/bgrins/TinyColor/blob/v2/src/random.ts )
let seededRandom_original = (max, min) => {
	max = max || 1;
	min = min || 0;

	Math.seed = (Math.seed * 9301 + 49297) % 233280;
	var rnd = Math.seed / 233280.0;

	return min + rnd * (max - min);
};

Timing test showed "2147483648" (3rd combo) to be faster than "4294967296" (2nd combo)... but visible tests show 3rd repeats very early.
IN CONCLUSION, if PERFECTION re. periodization is most important use 2nd combo (4294967296) else 1st (233280, same speed as 2147483648 aka 3rd combo)

let createRandomWithSeed_FASTER_REPEATS_EARLY=s=>(s=Math.abs(isNaN(s)?Date.now():s),_=>(s=(9301*s+49297)%233280,s/233280));
let createRandomWithSeed_SLOWER_REPEATS_LATER=s=>(s=Math.abs(isNaN(s)?Date.now():s),_=>(s=(1664525*s+1013904223)%4294967296,s/4294967296));
// let rnd = createRandomWithSeed(SEED); // then use rnd() instead of Math.random()