Find property by name in a deep object

a pure JavaScript solution would look like the following:

function findNested(obj, key, memo) {
  var i,
      proto = Object.prototype,
      ts = proto.toString,
      hasOwn = proto.hasOwnProperty.bind(obj);

  if ('[object Array]' !== ts.call(memo)) memo = [];

  for (i in obj) {
    if (hasOwn(i)) {
      if (i === key) {
        memo.push(obj[i]);
      } else if ('[object Array]' === ts.call(obj[i]) || '[object Object]' === ts.call(obj[i])) {
        findNested(obj[i], key, memo);
      }
    }
  }

  return memo;
}

here's how you'd use this function:

findNested({'aa': 1, 'bb': 2, 'cc': {'d':{'x':9}}, dd:{'d':{'y':9}}}, 'd');

and the result would be:

[{x: 9}, {y: 9}]

This should do it:

function fn(obj, key) {
    if (_.has(obj, key)) // or just (key in obj)
        return [obj];
    // elegant:
    return _.flatten(_.map(obj, function(v) {
        return typeof v == "object" ? fn(v, key) : [];
    }), true);

    // or efficient:
    var res = [];
    _.forEach(obj, function(v) {
        if (typeof v == "object" && (v = fn(v, key)).length)
            res.push.apply(res, v);
    });
    return res;
}