如何将三个js对象居中到DIV中：

<div id="container"></div>

#container {
  display: flex;
  justify-content: center;
  align-items: center;
}

var obj1 = document.createElement("div");
obj1.innerHTML = "Object 1";
document.getElementById("container").appendChild(obj1);

var obj2 = document.createElement("div");
obj2.innerHTML = "Object 2";
document.getElementById("container").appendChild(obj2);

var obj3 = document.createElement("div");
obj3.innerHTML = "Object 3";
document.getElementById("container").appendChild(obj3);