shuffle-seed/shuffle-seed.js

Shuffle Array based on a Seed

;(function() {
	var self = {};

	if(Math.seedrandom) seedrandom = Math.seedrandom;

	var isArray = function($){
		return Object.prototype.toString.call( $ ) === '[object Array]'
	}

	var extend = function(obj) {
		for (var i = 1; i < arguments.length; i++) for (var key in arguments[i]) obj[key] = arguments[i][key];
		return obj;
	}

	var seedify = function(seed){
		if (/(number|string)/i.test(Object.prototype.toString.call(seed).match(/^\[object (.*)\]$/)[1])) return seed;
		if (isNaN(seed)) return Number(String((this.strSeed = seed)).split('').map(function(x){return x.charCodeAt(0)}).join(''));
		return seed;
	}

	var seedRand = function(func,min,max){
		return Math.floor(func() * (max - min + 1)) + min;
	}

	self.shuffle = function(arr,seed){
		if (!isArray(arr)) return null;
		seed = seedify(seed) || 'none';

		var size = arr.length;
		var rng = seedrandom(seed);
		var resp = [];
		var keys = [];

		for(var i=0;i<size;i++) keys.push(i);
		for(var i=0;i<size;i++){
			var r = seedRand(rng,0,keys.length-1);
			var g = keys[r];
			keys.splice(r,1);
			resp.push(arr[g]);
		}
		return resp;
	}

	self.unshuffle = function(arr,seed){
		if (!isArray(arr)) return null;
		seed = seedify(seed) || 'none';

		var size = arr.length;
		var rng = seedrandom(seed);
		var resp = [];
		var map = [];
		var keys = [];

		for(var i=0;i<size;i++) {
			resp.push(null);
			keys.push(i);
		}

		for(var i=0;i<size;i++){
			var r = seedRand(rng,0,keys.length-1);
			var g = keys[r];
			keys.splice(r,1);
			resp[g]=arr[i];
		}

		return resp;
	}

	if(typeof exports!=='undefined'){
		module.exports=self;
	} else {
		this['shuffleSeed']=self;
	}
}.call(this));