given a seed value "iv" (optional), returns a deterministic string of pseudo-random hex values of length "chars"

spritzstream.js

// public domain, based on https://www.schneier.com/blog/archives/2014/10/spritz_a_new_rc.html

function spritzStream(chars, iv) {
	var s = [], key=iv || (Date.now() / (performance.now()*1000)).toString(36) + (chars/Math.random()),
		j = 0,
		w = 17,
		k = 0,
		res = [],
		l = Math.ceil(key.length/2),
		m = chars,
		z, x, i, y;

	for(i = 0; i < 256; i++) s[i] = i;

	for(i = 0; i < 256; i++) {
		j = (j + s[i] + key.charCodeAt(i % l)) % 256;
		x = s[i];
		s[i] = s[j];
		s[j] = x;
	}

	for(y = 0, i = 0, j = 0; y < m; y++) {
		i = (i + w) % 256;
		j = (k + s[j + s[i]]) % 256;
		k = (i + k + s[j]) % 256;
		x = s[i];
		s[i] = s[j];
		s[j] = x; //swap step
		res.push( (0+(z = (y%255) ^ s[j + s[i + s[z + k]]]).toString(16)).slice(-2));
	}
	return res.join("").slice(0, chars);
}

//ex:
//spritzStream(500, "this is not a great iv");