JavaScript游戏-如何控制子div不移动到它的父容器之外

var parentContainer = document.getElementById("parentContainer");
var childDiv = document.getElementById("childDiv");

parentContainer.addEventListener("mousemove", function(event) {
  // 在这里处理子div的位置
});

var parentLeft = parentContainer.offsetLeft;
var parentTop = parentContainer.offsetTop;
var mouseX = event.clientX;
var mouseY = event.clientY;

// 计算子div的新位置
var newLeft = mouseX - parentLeft;
var newTop = mouseY - parentTop;

var parentWidth = parentContainer.offsetWidth;
var parentHeight = parentContainer.offsetHeight;
var childWidth = childDiv.offsetWidth;
var childHeight = childDiv.offsetHeight;

// 限制子div的位置不超出父容器的边界
if (newLeft < 0) {
  newLeft = 0;
} else if (newLeft + childWidth > parentWidth) {
  newLeft = parentWidth - childWidth;
}

if (newTop < 0) {
  newTop = 0;
} else if (newTop + childHeight > parentHeight) {
  newTop = parentHeight - childHeight;
}

childDiv.style.left = newLeft + "px";
childDiv.style.top = newTop + "px";