尝试让蓝色正方形跟随红色正方形，但它不起作用

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

#container {
  position: relative;
  width: 400px;
  height: 400px;
}

#redSquare, #blueSquare {
  position: absolute;
  width: 50px;
  height: 50px;
}

#redSquare {
  background-color: red;
}

#blueSquare {
  background-color: blue;
}

var redSquare = document.getElementById("redSquare");
var blueSquare = document.getElementById("blueSquare");

redSquare.addEventListener("mousemove", function(event) {
  var x = event.clientX;
  var y = event.clientY;
  
  blueSquare.style.left = x + "px";
  blueSquare.style.top = y + "px";
});