Provide power set with recursive function calls.

recursive_power_set.js

var power_set = function (set) {
  var array=[[]],
  sub_set = function(n,m) {
    // should return 2 dimensions array                                                                     
    var result = [];

    if (m==1) {
      result.push([set[n]]);
    } else {
      for(var i=n, length=set.length; i<length-1; i+=1) {
        var subset = sub_set(i+1, m-1);
        for (var j=0; j<subset.length; j+=1) {
          var new_set = subset[j];
          new_set.push(set[n]);
          result.push(new_set);
        }
      }
    }
    return result;
  };

  for(var i=0, length=set.length; i<length; i+=1) {
    for (var j=1; j<length+1; j+=1) {
      var temp = sub_set(i, j);
      for (var k=0; k<temp.length; k+=1) {
        array.push(temp[k]);
      }
    }
  }
  return array;
};