how to insert multiple json data with single key in redis

i am new one for redis today only i have stared to work on this. i have inserted data into redis by done like this

  var data = {
      "name": "XXXxxx",
      "email": "xxxxx@gmail.com"
  }
  db.set('userdetails', JSON.stringify(data), function (err, result) {
      console.log(result);
  });

it inserted fine but when i try to insert new data i could view my newly inserted data but i could not view previously inserted data . how to insert multiple json data by using only one key(userdetails)? is there possible to create data structure like this?

userdetails:

[
    {
        "name": "xxxxxxxxxxxxxx",
        "email": "xxxxxx@gmail.com"
    }, {
        "name": "xxxxxxxxxx",
        "email": "xxxxxxx@gmail.com"
    }, {
        "name": "xxxxxx",
        "email": "xxxxxxxxx@gmail.com"
    }
]