sym.js

function sym() {

	var args = Array.prototype.slice.call(arguments);
	var flattened;

	if (args.length>1){
		flattened = args.reduce(function(previousValue, currentValue) {

			var pre = clearIntersection (previousValue,true);
			var cur = clearIntersection (currentValue,true);
			var res = clearIntersection(pre.concat(cur));
			console.log(pre+"-"+cur+"="+res);

			return res;
		});
	} else {
		flattened = clearIntersection (args[0],true);
	}


	function clearIntersection(flattened,saveOne){
		for (var outi = 0; outi < flattened.length; outi++){
			for (var ini = 0; ini <  flattened.length; ini++){
				if (outi!==ini && flattened[outi]===flattened[ini]){
					if (saveOne){
						flattened[outi] = null;
					} else{
						flattened[outi]=flattened[ini] = null;
					}

				}
			}  
		}
		return  cleanNull(flattened);
	}

	function cleanNull(flattened){
		for (var cleanI = 0; cleanI <  flattened.length; cleanI++){
			if (flattened[cleanI]===null){
				flattened.splice(cleanI, 1); 
				cleanI--;
			}
		}
		return flattened;
	}
	return flattened;
}