JS实现图片拖拽交换效果，供大家参考，具体内容如下
听 WEB前端javascript企业实战班 公开课，用JS实现了图片拖拽交换的目的；感谢老师的讲解。
实现要点
鼠标点击onmousedown：获取鼠标在页面上可视区域的位置(clientX, clientY)和元素外边框距已定位父元素容器的位置(offsetLeft,offsetTop)；
鼠标移动onmousemove: 获取鼠标在页面上可视区域的位置(clientX, clientY),并实时改变目标元素位置；进行碰撞检测，同时计算被碰撞元素与目标元素中心点距离，将距离最小的定位交换元素；
鼠标释放onmouseup: 进行元素交换
注意点
排除没有碰撞成功的情况，进行特殊讨论；
覆盖html5原有的图片拖拽功能，通过return false返回；
交换时同时勿忘记交换图片的索引；
小技巧
进行碰撞检测时，可以进行逆向思维，检测未碰撞的情况，即判断目标元素是否超过碰撞元素的边界(如：目标元素的右侧是否超过被碰撞元素的左侧)
计算元素中心位置时，可以改为计算元素左上角之间的距离，从而转变为计算(offsetLeft1,offsetTop1)(offsetLeft1,offsetTop1)与(offsetLefti(offsetLefti, offsetTopi)offsetTopi)的距离,以简化计算；
实现
HTML
<div> <ul> <li><img src="" alt=""></li> <li><img src="" alt=""></li> <li><img src="" alt=""></li> <li><img src="" alt=""></li> <li><img src="" alt=""></li> <li><img src="" alt=""></li> <li><img src="" alt=""></li> <li><img src="" alt=""></li> <li><img src="" alt=""></li> </ul> </div>
CSS
* { margin:0; padding: 0; } body { user-select: none; /*阻止文本选中*/ } #photo { width: 600px; height: 600px; border: 2px solid #000; margin: 20px auto; } #photo ul li { list-style:none; width: 180px; height: 180px; margin: 10px; float: left; } #photo ul li:hover { background: #c0c; } #photo ul li img { width: 180px; height: 180px; border: 1px solid #ccc; }
JS
var photo = document.getElementById("photo"); var oUl = photo.getElementsByTagName("ul")[0]; var aLi = oUl.getElementsByTagName("li"); var z = 2; var arr = []; for (var i = 0; i < aLi.length; i++) { arr.push([aLi[i].offsetLeft, aLi[i].offsetTop]); } for (var i = 0; i < aLi.length; i++) { aLi[i].style.position = "absolute"; aLi[i].style.left = arr[i][0] + "px"; aLi[i].style.top = arr[i][1] + "px"; aLi[i].style.margin = 0; } for (var i = 0; i < aLi.length; i++) { aLi[i].index = i; drag(aLi[i]); } function drag(obj) { obj.onmousedown = function(ev) { ev = ev || window.ev; var x = ev.clientX; var y = ev.clientY; var l = obj.offsetLeft; var t = obj.offsetTop; this.style.zIndex = z++; document.onmousemove = function(ev) { ev = ev || window.ev; var _left = ev.clientX - x + l; var _top = ev.clientY - y + t; obj.style.left = _left + "px"; obj.style.top = _top + "px"; var li = near(obj); for (var i = 0; i < aLi.length; i++) { aLi[i].style.background = ""; } if (li) { li.style.background = "#DF971F"; } } document.onmouseup = function() { document.onmousemove = null; document.onmousedown = null; var nearLi = near(obj); var tmp = 0; if (nearLi) { move(nearLi, {left:arr[obj.index][0], top:arr[obj.index][1]}); move(obj, {left:arr[nearLi.index][0], top:arr[nearLi.index][1]}); nearLi.style.background = ""; tmp = obj.index; obj.index = nearLi.index; nearLi.index = tmp; } else { move(obj, {left:arr[obj.index][0], top:arr[obj.index][1]}); } } return false; } } function impact(obj1, obj2) { var L1 = obj1.offsetLeft; var R1 = obj1.offsetLeft + obj1.offsetWidth; var T1 = obj1.offsetTop; var B1 = obj1.offsetTop + obj1.offsetHeight; var L2 = obj2.offsetLeft; var R2 = obj2.offsetLeft + obj2.offsetWidth; var T2 = obj2.offsetTop; var B2 = obj2.offsetTop + obj2.offsetHeight; if (L2 > R1 || T2 > B1 || R2 < L1 || B2 < T1) { return false; } else { return true; } } function near(obj) { var tmp = 5000; var oLi = ''; for (var i = 0; i < aLi.length; i++) { if (impact(obj, aLi[i]) && obj != aLi[i]) { var c = disCalc(obj, aLi[i]); if (tmp > c) { tmp = c; oLi = aLi[i]; } } } return oLi; } function disCalc(obj1, obj2) { var x = obj1.offsetLeft - obj2.offsetLeft; var y = obj1.offsetTop - obj2.offsetTop; return Math.sqrt(x * x + y * y); }
move.js
function move(obj, json, endFn) { clearInterval(obj.timer); obj.timer = setInterval(function() { var bBtn = true; for (var attr in json) { var iCur = 0; if (attr == 'opacity') { if (Math.round(parseFloat(getStyle(obj,attr)) * 100) == 0) { iCur = Math.round(parseFloat(getStyle(obj,attr)) * 100); } else { iCur = Math.round(parseFloat(getStyle(obj,attr)) * 100) || 100; } } else { iCur = parseInt(getStyle(obj,attr)) || 0; } var iSpeed = (json[attr] - iCur) / 8; iSpeed = iSpeed >0 ? Math.ceil(iSpeed) : Math.floor(iSpeed); if (iCur != json[attr]) { bBtn = false; } if (attr == 'opacity') { obj.style.filter = 'alpha(opacity=' +(iCur + iSpeed)+ ')'; obj.style.opacity = (iCur + iSpeed) / 100; } else { obj.style[attr] = iCur + iSpeed + 'px'; } } if (bBtn) { clearInterval(obj.timer); if (endFn) { endFn.call(obj); } } }, 30); } function getStyle(obj, attr) { if (obj.currentStyle) { return obj.currentStyle[attr]; } else { return getComputedStyle(obj, false)[attr]; } }