Javascript Number formatString(num, comma)

/* Extended JavaScript Number library
 * Copyright 2009 Jaakko-Heikki Heusala <jheusala@iki.fi>
 * $Id: $/* w  w w.  j a v  a2s .c o  m*/
 */

/* Format number */
Number.prototype.formatString = function(num, comma) {
 return this.toFixed(num).toString().replace(/\.([0-9]*)$/, comma+"$1");
}