How do I deal with strings?

Code:
function fn1(hh3,hm3,hs3){
     HMS3 = hh3 & "h" & hm3 & "m" & hs3 & "s";
     return HMS3;
}

function HMS(){
     hh30 = Number(window.document.myform.hh3.value);
     hm30 = Number(window.document.myform.hm3.value);
     hs30 = Number(window.document.myform.hs3.value);
     str = fn1(hh30,hm30,hs30);
     window.document.myform.dmsd3.value = str;
}