<script>
 window.onload = function() {
  var oUl = document.getElementById("ul1");
  var aLi = oUl.getElementsByTagName("li");
  var disX = 0;
  var disY = 0;
  var minZindex = 1;
  var aPos = [];
  for (var i = 0; i < aLi.length; i++) {
   var t = aLi[i].offsetTop;
   var l = aLi[i].offsetLeft;
   aLi[i].style.top = t + "px";
   aLi[i].style.left = l + "px";
   aPos[i] = {
    left: l,
    top: t
   };
   aLi[i].index = i;
  }
  for (var i = 0; i < aLi.length; i++) {
   aLi[i].style.position = "absolute";
   aLi[i].style.margin = 0;
   setDrag(aLi[i]);
  }
  //拖拽
  function setDrag(obj) {
   obj.onmouseover = function() {
    obj.style.cursor = "move";
   }
   obj.onmousedown = function(event) {
    var scrollTop = document.documentElement.scrollTop || document.body.scrollTop;
    var scrollLeft = document.documentElement.scrollLeft || document.body.scrollLeft;
    obj.style.zIndex = minZindex++;
    //當鼠標按下時計算鼠標與拖拽對象的距離
    disX = event.clientX + scrollLeft - obj.offsetLeft;
    disY = event.clientY + scrollTop - obj.offsetTop;
    document.onmousemove = function(event) {
     //當鼠標拖動時計算div的位置
     var l = event.clientX - disX + scrollLeft;
     var t = event.clientY - disY + scrollTop;
     obj.style.left = l + "px";
     obj.style.top = t + "px";
     /*for(var i=0;i<aLi.length;i++){
     	aLi[i].className = "";
     	if(obj==aLi[i])continue;//如果是自己則跳過自己不加紅色虛線
     	if(colTest(obj,aLi[i])){
     		aLi[i].className = "active";
     	}
     }*/
     for (var i = 0; i < aLi.length; i++) {
      aLi[i].className = "";
     }
     var oNear = findMin(obj);
     if (oNear) {
      oNear.className = "active";
     }
    }
    document.onmouseup = function() {
     document.onmousemove = null; //當鼠標彈起時移出移動事件
     document.onmouseup = null; //移出up事件，清空內存
     //檢測是否普碰上，在交換位置
     var oNear = findMin(obj);
     if (oNear) {
      oNear.className = "";
      oNear.style.zIndex = minZindex++;
      obj.style.zIndex = minZindex++;
      startMove(oNear, aPos[obj.index]);
      startMove(obj, aPos[oNear.index]);
      //交換index
      oNear.index += obj.index;
      obj.index = oNear.index - obj.index;
      oNear.index = oNear.index - obj.index;
     } else {

      startMove(obj, aPos[obj.index]);
     }
    }
    clearInterval(obj.timer);
    return false; //低版本出現禁止符號
   }
  }
  //碰撞檢測
  function colTest(obj1, obj2) {
   var t1 = obj1.offsetTop;
   var r1 = obj1.offsetWidth + obj1.offsetLeft;
   var b1 = obj1.offsetHeight + obj1.offsetTop;
   var l1 = obj1.offsetLeft;

   var t2 = obj2.offsetTop;
   var r2 = obj2.offsetWidth + obj2.offsetLeft;
   var b2 = obj2.offsetHeight + obj2.offsetTop;
   var l2 = obj2.offsetLeft;

   if (t1 > b2 || r1 < l2 || b1 < t2 || l1 > r2) {
    return false;
   } else {
    return true;
   }
  }
  //勾股定理求距離
  function getDis(obj1, obj2) {
   var a = obj1.offsetLeft - obj2.offsetLeft;
   var b = obj1.offsetTop - obj2.offsetTop;
   return Math.sqrt(Math.pow(a, 2) + Math.pow(b, 2));
  }
  //找到距離最近的
  function findMin(obj) {
   var minDis = 999999999;
   var minIndex = -1;
   for (var i = 0; i < aLi.length; i++) {
    if (obj == aLi[i]) continue;
    if (colTest(obj, aLi[i])) {
     var dis = getDis(obj, aLi[i]);
     if (dis < minDis) {
      minDis = dis;
      minIndex = i;
     }
    }
   }
   if (minIndex == -1) {
    return null;
   } else {
    return aLi[minIndex];
   }
  }
 }
</script>

 

<ul id="ul1">
 <li><img src="https://www.jq22.com/img/cs/500x500-1.png" width="200" height="150 "></li>
  <li><img src="https://www.jq22.com/img/cs/500x500-2.png " width="200 " height="150 "></li>
  <li><img src="https://www.jq22.com/img/cs/500x500-3.png " width="200 " height="150 "></li>
  <li><img src="https://www.jq22.com/img/cs/500x500-4.png " width="200 " height="150 "></li>
  <li><img src="https://www.jq22.com/img/cs/500x500-5.png " width="200 " height="150 "></li>
  <li><img src="https://www.jq22.com/img/cs/500x500-6.png " width="200 " height="150 "></li>
 </ul>

* {
	margin:0;
	padding:0;
	list-style:none
}
#ul1 {
	width:660px;
	position:relative;
	margin:10px auto;
}
#ul1 li {
	width:200px;
	height:150px;
	float:left;
	list-style:none;
	margin:10px;
}
#ul1 li:hover {
	border-color:#9a9fa4;
	box-shadow:0 0 6px 0 rgba(0,0,0,0.85);
}
#ul1 .active {
	border:1px dashed red;
}

//通過class獲取元素
function getClass(cls) {
 var ret = [];
 var els = document.getElementsByTagName("*");
 for (var i = 0; i < els.length; i++) {
  //判斷els[i]中是否存在cls這個className;.indexOf("cls")判斷cls存在的下標，如果下標>=0則存在;
  if (els[i].className === cls || els[i].className.indexOf("cls") >= 0 || els[i].className.indexOf(" cls") >= 0 || els[i].className.indexOf(" cls ") > 0) {
   ret.push(els[i]);
  }
 }
 return ret;
}

function getStyle(obj, attr) { //解決JS兼容問題獲取正確的屬性值
 return obj.currentStyle &#63; obj.currentStyle[attr] : getComputedStyle(obj, false)[attr];
}

function startMove(obj, json, fun) {
 clearInterval(obj.timer);
 obj.timer = setInterval(function() {
  var isStop = true;
  for (var attr in json) {
   var iCur = 0;
   //判斷運動的是不是透明度值
   if (attr == "opacity") {
    iCur = parseInt(parseFloat(getStyle(obj, attr)) * 100);
   } else {
    iCur = parseInt(getStyle(obj, attr));
   }
   var ispeed = (json[attr] - iCur) / 8;
   //運動速度如果大于0則向下取整，如果小于0想上取整；
   ispeed = ispeed > 0 &#63; Math.ceil(ispeed) : Math.floor(ispeed);
   //判斷所有運動是否全部完成
   if (iCur != json[attr]) {
    isStop = false;
   }
   //運動開始
   if (attr == "opacity") {
    obj.style.filter = "alpha:(opacity:" + (json[attr] + ispeed) + ")";
    obj.style.opacity = (json[attr] + ispeed) / 100;
   } else {
    obj.style[attr] = iCur + ispeed + "px";
   }
  }
  //判斷是否全部完成
  if (isStop) {
   clearInterval(obj.timer);
   if (fun) {
    fun();
   }
  }
 }, 30);
}