[KidsKilla]

var a = [1,2,3,4];
var b = [1,2,3,5,6]
var lost_data = a.concat();
var get_data = b.concat();
for(var i=a.length; --i>=0;){
	for(var j=b.length; --j>=0;){
        if (a[i] == b[j]) {
            lost_data.splice(i, 1);
            get_data.splice(j, 1);
            break;
        }
	}
}
trace(["lost[",lost_data,"] get[", get_data,"]"]);
trace([a," : ",b])