deepclone

function isObject(obj) {
  return !!obj && typeof obj === 'object';
}
function find(arr, key, target) {
  var len = arr.length;
  for (var i = 0; i < len; i++) {
    if (!arr[i]) continue;
    if (arr[i][key] === target) return arr[i];
  }
}
function deepClone(object) {
  var objects = [];
  var count = 0;
  function _deepClone(obj) {
    count++;
    if (count > 100) {
      throw new Error('probably too deep to clone..')
    }
    var res = {};
    objects.push({
      source: obj,
      dest: res
    });
    Object.keys(obj).forEach(function(k) {
       if (isObject(obj[k])) {
         var j = find(objects, 'source', obj[k]);
         if (j) { res[k] = j.dest; return; }
         res[k] = _deepClone(obj[k]);
       } else {
         res[k] = obj[k];
       }
    });
    return res;
  }
  return _deepClone(object);
}