Why wont this javascript function work?

[Red Squirrel]

function lzero(str, len) 
{
  str += ''; // cast to string
  
  while(str.length < len)
  {
	  str = "0".str;
  }
  
  return str;
}

When the value of str passed to the function is 0 to 9, I get the error "TypeError: str is undefined" for the while loop. Why is this?

I just want to add leading zeros to a number. Is there maybe a better way?

 

[Ken g6]

You appear to be confusing your concatenation operators. The string "0" does not have a property "str".

 

[Red Squirrel]

Oh so it thinks I want to access a property? How do I force it to actually concatenate? Figured the quotes would do as variables don't have quotes. Also the odd part is that I got this off the internet, and most examples I find are similar, and none work.

edit:

OHHHHh it's + and not . I was being confused, and guess the first example I found was wrong or maybe was for php (said javascript though). I got it now, thanks. Never even thought the issue was after the error.

 

[DaveSimmons]

PHP = .
javacript = +

... which can be confusing if you're working with both languages at the same time