JS: functions similar to PHP's "substr()" and "strlen()" [nevermind]

I'm not really into JS at all, but I'm working on something and since I have no idea of the JS functions or where to find an index of them, I decided I'd ask here. I'm looking for a function similar to PHP's substr() function. If you don't know what the substr() function does; I'll try to explain.

substr()

Syntax: substr(str string, int start pos [, int length]);

Purpose: Returns part of string specified by the start pos and length parameters.

Usage:

PHP Code:

---

<?
  $var = "12345";
  echo substr($var, 1, 2);
?>

---

This will print: 23

I'm also looking for a function similar to PHP's strlen() function, which just returns the number of characters in a string.

Any help is appreciated.

edit: nevermind, found what I needed.