尝试获取JS画布中点与鼠标之间的距离

Question

因此，我用centerX和centerY获得了该点的中心，我想获得该点与鼠标之间的距离。

我收到一条错误消息，说clientX不起作用。

function dist(event){
  var rect = canvas.getBoundingClientRect();
  var mouseX = event.clientX - rect.left;
  var mouseY = event.clientY - rect.top;

  var a = centerX - mouseX;
  var b = centerY - mouseY;

  var dist = Math.hypot(a, b);
  if(dist <= 50){
    alert("test");
  }
}