Join strings together in loop

1

this should be easy but cannot get it to work:

[AS]var newXML;
for(var i = 0; i < oldXML.length; i++) {
// join child nodes together in string var called newXML
newXML = newXML + myXML.firstChild.firstChild.childNodes*;
}
trace(newXML); [/AS]

have tried a number of methods including concat(), & etc. I know I’ll kick myself . . .