代码如下：
<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <title>登录框鼠标拖拽效果</title> <style type="text/css"> body { background: url("https://timgsa.baidu.com/timg?image&quality=80&size=b9999_10000&sec=1488778794834&di=e97c96dfe7860297d1968c30adc862a2&imgtype=0&src=http%3A%2F%2Fpic1.5442.com%3A82%2F2015%2F0409%2F01%2F15.jpg%2521960.jpg") no-repeat top center #ffffff; background-size: 100%; padding: 0; margin: 0; font-size: 12px; font-family: "微软雅黑", sans-serif; } .ui-dialog { width: 380px; position: absolute; z-index: 9000; top: 100px; left: 100px; border: 1px solid #d5d5d5; background-color: #ffffff; /*display: none;*/ } .ui-dialog-title { height: 48px; line-height: 48px; padding-left: 20px; color: #535353; font-size: 16px; background-color: #f5f5f5; border-bottom: 1px solid #efefef; cursor: move; } .ui-dialog-title-closebutton { width: 16px; height: 16px; display: inline-block; position: absolute; right: 20px; color: #000; text-decoration: unset; } .ui-dialog-title-closebutton:hover { color: #4ca8ff; } .ui-dialog-content { padding: 15px 20px; } .ui-dialog-pt15 { padding-top: 15px; } .ui-dialog-l40 { height: 40px; line-height: 40px; text-align: right; } .ui-dialog-input { width: 100%; height: 40px; margin: 0; padding: 0; border:1px solid #d5d5d5; font-size: 16px; color: #c1c1c1; text-indent: 25px; outline: none; } .ui-dialog-input-username { background: url("images/input_username.png") no-repeat 2px; } .ui-dialog-input-password { background: url("images/input_password.png") no-repeat 2px; } .ui-dialog-submit { width: 100%; height: 50px; background: #3b7ae3; border: none; font-size: 16px; color: #ffffff; outline: none; text-decoration: none; display: block; text-align: center; line-height: 50px; } .ui-dialog-submit:hover { background: #3f81b0; } .ui-mask { width: 100%; height: 100%; background: #000; opacity: 0.4; position: absolute; top: 0; left: 0; z-index: 8000; display: none; } .link { text-align: right; line-height: 20px; padding-right: 40px; } </style> </head> <body> <div> <div> 登录 <!-- 右上角的关闭按钮 --> <a href="javascript:hideDialog();">X</a> </div> <div> <div> <input type="input" placeholder="手机/邮箱/用户名" /> </div> <div> <input type="input" placeholder="密码" /> </div> <div> <a href="#" >忘记密码</a> </div> <div> <a href="#" >登录</a> </div> <div> <a href="#" >立即注册</a> </div> </div> </div> <div></div> <div> <a href="javascript:showDialog();">登录</a> </div> <script type="text/javascript"> // 获取元素对象 function g(id) { return document.getElementById(id); } // 自动居中函数 -- 登录浮层 // el {Element} function autoCenter(el) { // 获得可视区域的宽和高 var bodyW = document.documentElement.clientWidth; var bodyH = document.documentElement.clientHeight; // 获得元素 el 的宽和高 var elW = el.offsetWidth; var elH = el.offsetHeight; // 设置元素的 style 样式 el.style.left = (bodyW - elW) / 2 + 'px'; el.style.top = (bodyH - elH) / 2 + 'px'; } // 扩展元素到整个可视区域 -- 遮罩层 // el {Element} function fillToBody(el) { // 将元素的宽和高设置的和可视区域一样 el.style.width = document.documentElement.clientWidth + 'px'; el.style.height = document.documentElement.clientHeight + 'px'; } // 定义全局变量 var mouseOffsetX = 0; var mouseOffsetY = 0; var isDragging = false; // 鼠标事件1 -- 在标题栏上按下 // 计算鼠标相对拖拽元素的的左上角的坐标， 并且标记元素为可拖动 g('dialogTitle').addEventListener('mousedown', function(e) { var e = e || window.event; // 用鼠标按下时的坐标减去 dialog 的左上角坐标 mouseOffsetX = e.pageX - g('dialog').offsetLeft; mouseOffsetY = e.pageY - g('dialog').offsetTop; isDragging = true; }); // 鼠标事件2 -- 鼠标移动 document.onmousemove = function(e) { var e = e || window.event; // 鼠标当前位置 var mouseX = e.pageX; var mouseY = e.pageY; // 鼠标从单击时至当前时刻移动的距离 var moveX = 0; var moveY = 0; if (isDragging === true) { moveX = mouseX - mouseOffsetX; moveY = mouseY - mouseOffsetY; // 范围限定 // moveX > 0 且 moveX < (页面最大宽度 - 浮层宽度) // moveY > 0 且 moveY < (页面最大宽度 - 浮层高度) var pageWidth = document.documentElement.clientWidth; var pageHeight = document.documentElement.clientHeight; // 登录浮层的宽、高 var dialogWidth = g('dialog').offsetWidth; var dialogHeight = g('dialog').offsetHeight; var maxX = pageWidth - dialogWidth; var maxY = pageHeight - dialogHeight; moveX = Math.min(maxX, Math.max(0, moveX)); moveY = Math.min(maxY, Math.max(0, moveY)); g('dialog').style.left = moveX + 'px'; g('dialog').style.top = moveY + 'px'; } }; // 鼠标事件3 -- 鼠标松开 document.onmouseup = function() { isDragging = false; }; // 展现登录浮层 function showDialog() { g('dialog').style.display = 'block'; g('mask').style.display = 'block'; autoCenter(g('dialog')); fillToBody(g('mask')); } // 隐藏登录浮层 function hideDialog() { g('dialog').style.display = 'none'; g('mask').style.display = 'none'; } window.onresize = function() { autoCenter(g('dialog')); fillToBody(g('mask')); }; showDialog(); autoCenter(g('dialog')); </script> </body> </html>