function test() {
var a = new Array();
for (var i=0; i<1000; i++) {
a[i] = i + 'a';
}
var loops = 500;
var str = "";
before = new Date();
for (var i=0; i<loops; i++) {
str = a.join('-');
}
after = new Date();
time = (after-before);
result(time, str);
}

Time:

Resulting String