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                <div id="box"></div>


                #box {
  width: 200px;
  height: 200px;
  background-color: pink;
  position: relative;


                function getStyleNum(el, style) {
  return parseInt(window.getComputedStyle(el)[style])
window.onload = function () {
  let box = document.getElementById("box")
  let dragging = false
  // 记录鼠标初始位置
  let mouseStartPos = { x: 0, y: 0 }
  // 记录元素初始位置
  let elStartPos = { x: 0, y: 0 }
  box.addEventListener("mousedown", function (e) {
    dragging = true = "relative"
    // 获取鼠标点击的位置
    mouseStartPos.x = e.clientX
    mouseStartPos.y = e.clientY
    // 获取当前元素的位置
    elStartPos.x = getStyleNum(box, "left")
    elStartPos.y = getStyleNum(box, "top")
  box.addEventListener("mousemove", function (e) {
    if (dragging) {
      // 计算鼠标在拖拽过程中的偏移量
      let offset = {
        x: e.clientX - mouseStartPos.x,
        y: e.clientY - mouseStartPos.y
      // 将偏移量与元素开始时的位置相计算得出元素的实时位置 = elStartPos.x + offset.x + "px" = elStartPos.y + offset.y + "px"
  // 鼠标移出元素或者抬起时停止拖拽
  box.addEventListener("mouseup", function (e) {
    dragging = false
  box.addEventListener("mouseout", function (e) {
    dragging = false