Javascript Array sum( iterator )

/**/*  w  w  w. j a  v  a  2  s. co m*/
* Paste bin for general JavaScript language extensions to be compiled into the production
* and lexically scoped out via an anonomous function.
*/


// sum fn extension to the Array object can recursive sum up array values
Array.prototype.sum = function ( iterator ) {
 "use strict";
 var i = ( typeof iterator === "undefined" ) ?  0 : iterator,
  total = 0;

 // check for nested array structure
 if ( this[ i ] instanceof Array ) {
  for ( i; i < this.length; i++) {
   // now sum rows by recursing into this fn
   total += this[i].sum();
  }
 }
 else {
 // not a nested structure
  for (i = 0; i < this.length; i++) {
   total += this[i];
  }
 }

 return total;
};