QQ面板拖拽，效果如图

JavaScript代码如下：

function getByClass(clsName, parent) { var oParent = parent ? document.getElementById(parent) : document, eles = [], elements = oParent.getElementsByTagName('*'); for (var i = 0, l = elements.length; i < l; i++) { if (elements[i].className == clsName) { eles.push(elements[i]); } } return eles;}window.onload = drag;function drag() { var oTitle = getByClass("login_logo_webqq", "loginPanel")[0]; //拖页 oTitle.onmousedown = fnDown; //关闭页面 var close = document.getElementById("ui_boxyClose"); close.onclick = winClose; //切换状态 var loginState = document.getElementById("loginState"); var stateList = document.getElementById("loginStatePanel"); var lis = stateList.getElementsByTagName("li"); var stateTxt = document.getElementById("login2qq_state_txt"); var loginStateShow = document.getElementById("loginStateShow"); //点击显示下拉单 loginState.onclick = function (e) { stateList.style.display = "block"; //阻止事件冒泡； e = event || window.event; if(e.stopPropagation){ e.stopPropagation(); }else{ e.cancelBubble = true; } }; //鼠标滑过,背景变色 for (var i = 0; i < lis.length; i++) { lis[i].onmouseover = function () { this.style.backgroundColor = "#888"; }; lis[i].onmouseout = function () { this.style.backgroundColor = "#fff"; }; //鼠标点击，txt改变，图标改变 lis[i].onclick = function (e) { stateList.style.display = "none"; //阻止事件冒泡 e = event || window.event; if(typeof e.stopPropagation){ e.stopPropagation(); }else { e.cancelBubble = true; } var id = this.id; loginStateShow.className = "login-state-show "+id; var text = getByClass("stateSelect_text",id)[0].innerHTML; stateTxt.innerHTML = text; } } document.onclick = function () { stateList.style.display = "none"; }}function winClose() { var box = document.getElementById("loginPanel"); box.style.display = "none";}function fnDown(event) { var event = event || window.event; var oDrag = document.getElementById("loginPanel"); //光标按下时光标和面板之间的距离； var disX = event.clientX - oDrag.offsetLeft; var disY = event.clientY - oDrag.offsetTop; //移动 document.onmousemove = function (event) { event = event || window.event; fnMove(event, disX, disY); }; document.onmouseup = function () { document.onmousemove = null; document.onmouseup = null; }}function fnMove(event, posX, posY) { var oDrag = document.getElementById("loginPanel"); var l = event.clientX - posX; var t = event.clientY - posY; var winW = document.documentElement.clientWidth; var winH = document.documentElement.clientHeight; var maxW = winW - oDrag.offsetWidth - 10; var maxH = winH - oDrag.offsetHeight; //当l=0时，窗口不能继续外移 if (l < 0) { l = 0; } else if (l > maxW) { l = maxW; } if (t < 10) { t = 10; } else if (t > maxH) { t = maxH; } oDrag.style.left = l + "px"; oDrag.style.top = t + "px";}

要点：

1.阻止事件冒泡

loginState.onclick点击事件冒泡，导致下拉列表无法点开

loginState.onclick = function () { stateList.style.display = "block";}document.onclick = function () { stateList.style.display = "none";}

lis[i].onclick列表项的点击事件冒泡，导致下拉列表无法隐藏

lis[i].onclick = function () { stateList.style.display = "none";}loginState.onclick = function () { stateList.style.display = "block";}

2.鼠标事件坐标获取

function fnDown(event) { var event = event || window.event; var oDrag = document.getElementById("loginPanel"); //光标按下时光标和面板之间的距离； var disX = event.clientX - oDrag.offsetLeft; var disY = event.clientY - oDrag.offsetTop; //移动 document.onmousemove = function (event) { event = event || window.event; fnMove(event, disX, disY); }; document.onmouseup = function () { document.onmousemove = null; document.onmouseup = null; }}function fnMove(event, posX, posY) { var oDrag = document.getElementById("loginPanel"); var l = event.clientX - posX; var t = event.clientY - posY; var winW = document.documentElement.clientWidth; var winH = document.documentElement.clientHeight; var maxW = winW - oDrag.offsetWidth - 10; var maxH = winH - oDrag.offsetHeight; //当l=0时，窗口不能继续外移 if (l < 0) { l = 0; } else if (l > maxW) { l = maxW; } if (t < 10) { t = 10; } else if (t > maxH) { t = maxH; } oDrag.style.left = l + "px"; oDrag.style.top = t + "px";}

3.封装各浏览器通用的getElementsByClassName()方法

方法返回的是一个数组，切记

function getByClass(clsName, parent) { var oParent = parent ? document.getElementById(parent) : document, eles = [], elements = oParent.getElementsByTagName('*'); for (var i = 0, l = elements.length; i < l; i++) { if (elements[i].className == clsName) { eles.push(elements[i]); } } return eles;}

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