获取两个数组的相同元素或不相同的元素

var old:Array = new Array("a","b","c","a","d");
var now:Array = new Array("a","f","g","h");
for (var i=0; i<now.length; i++) {
var a = now[i];
for each (var item in old) {
if (old.indexOf(a) != -1) {
//old.splice(old.indexOf(a),1);
} else {
old.push(a);
trace("新值:" + a)
}
}

}
trace(old);//b,c,d
trace(now);