write script using loop

Question

1
12
123
1234
12345

Answer 1

var s = "";
for(var i = 1; i<=5; i++){
s += i;
document.writeln(s);
}

Answer 2

var num="";
for(var i=1 i<=5 i++){
num+=i;
document.write("num"+<br/>)
}
哇哈哈，很简单啊！