Learning Loops & Want To Produce A Number Sequence

I have no js experience or coding experience of any kind other than the last few hours of reading a book called 'object-oriented javascript', and all was well until loops. firstly, this is how he teaches the while loop...

var i = 0;
while (i <10)
{i++;}

which results in 9 we move on to for loops...

var res ='';
for( var i = 0; i <10; i++)
{res += 'sometext' ;}

which repeats, but I'd like to be able to make that into a sequence of numbers... 123456789.