String index in an Object

var source:Object = new Object();
source.col1 = "1";
source.col2 = "2";
source.col3 = "3";
source.col4 = "4";
source.col5 = "5";
var target:Object = new Object();
for(var i:String in source) {
    target[i] = source[i];
    trace(target[i]);
}