Javascript String split() method

/*//from  ww w.  j a  v  a 2s  .com
 * String
 */
String.prototype.oldSplit = String.prototype.split;

String.prototype.split = function (separator, limit) { 
 var parts = this.oldSplit(separator);
 
 if (!limit)
  return parts;
 
 // Take parts that should be split
 var newParts = parts.slice(0, limit - 1);
 
 // Concat parts that should be joined
 return newParts.concat(parts.slice(limit - 1).join(separator));
};

/*
 * Function
 */
Function.prototype.isA = function (parent) {
 this.prototype = parent;
 this.prototype.constructor = this;
};