eatarandom

/**
 * Converts "1000" to "1,000"
 */
String.prototype.addCommas = function() {
     var s = this, c = this.length-3;
     while(c>0){
          s = s.substr(0,c)+','+s.substr(c,s.length-1);
          c -= 3;
     }
     return s;