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                <div id="range">
  <div class="icon">100*100</div>


                #range {
  position: relative;
  width: 600px;
  height: 400px;
  margin: 10px;
  background-color: rgb(133, 246, 250);

.icon {
  position: absolute;
  height: 100px;
  width: 100px;
  cursor: move;
  background-color: #ff9204;
  user-select: none;


                const main = document.getElementById('range');
const icon = document.querySelector('.icon');
let move = false;
let deltaLeft = 0, deltaTop = 0;

icon.addEventListener('mousedown', function (e) {
  /** @des deltaLeft 即移动过程中不变的值 */
  deltaLeft =;
  deltaTop =;
  move = true;

main.addEventListener('mousemove', function (e) {
  if (move) {
    const cx = e.clientX;
    const cy = e.clientY;
    /** 相减即可得到相对于父元素移动的位置 */
    let dx = cx - deltaLeft
    let dy = cy - deltaTop

    /** 防止超出父元素范围 */
    if (dx < 0) dx = 0
    if (dy < 0) dy = 0
    if (dx > 500) dx = 500
    if (dy > 300) dy = 300
    icon.setAttribute('style', `left:${dx}px;top:${dy}px`)

main.addEventListener('mouseup', function (e) {
  move = false;