array dimension for javascript

gistfile1.js

//
// [1].dim() == 1
// [1,2].dim() == 1
// [[1]].dim() == 2
// [[1,2,3],4,[5,6,7],[8,9,0]].dim() == 2
// [[1,[2]],3,[[4,5],6,[7,8]]].dim() == 3
//

Array.prototype.dim = function dim() {
   return this.reduce(function(a,b) {
      return ( ((a.dim===dim&&a.dim()) || 0) ) + ( (b.dim===dim&&b.dim()) || 0 ) + 1;
   },0);
}