DOM提供了一套与元素自身有关的位置和大小的属性
偏移量属性
- offsetParent 偏移参考父级，距离自己最近的有定位的父级，如果都没有定位参考body(html)
- offsetLeft/offsetTop 偏移位置
- offsetWidth/offsetHeight 偏移大小
var child = document.getElementById("child");
// 元素天生就认识自己的偏移参考父级
console.log(child.offsetParent);
距离自己有定位的最近父级
偏移量属性参考图
client 系列属性/客户端大小
- client系列没有参考父级元素
- clientLeft/clientTop：边框区域尺寸，不常用
- clientWidth/clientHeight：边框内部大小
需要边框使用偏移量属性，不需要的话使用client属性
滚动偏移属性/scroll属性
- scrollLeft/scrollTop 盒子内部滚动出去的尺寸
-
scrollWidth/scrollHeight 盒子内容的宽度和高度
拖拽案例
示例图
<!DOCTYPE html>
<html>
<head lang="en">
<meta charset="UTF-8">
<title></title>
<style>
* {
margin: 0;
padding: 0;
}
.nav {
height: 30px;
background: #036663;
border-bottom: 1px solid #369;
line-height: 30px;
padding-left: 30px;
}
.nav a {
color: #fff;
text-align: center;
font-size: 14px;
text-decoration: none;
}
.d-box {
width: 400px;
height: 300px;
border: 5px solid #eee;
box-shadow: 2px 2px 2px 2px #666;
position: absolute;
top: 40%;
left: 40%;
background-color: white;
/* 不让文字被选中 */
-webkit-user-select:none;
-moz-user-select:none;
-ms-user-select:none;
user-select:none;
}
.hd {
width: 100%;
height: 25px;
background-color: #7c9299;
border-bottom: 1px solid #369;
line-height: 25px;
color: white;
cursor: move;
}
#box_close {
float: right;
cursor: pointer;
}
</style>
</head>
<body>
<div class="nav">
<a href="javascript:;" id="register">注册信息</a>
</div>
<div class="d-box" id="d_box">
<div class="hd" id="drop">注册信息 (可以拖拽)
<span id="box_close">【关闭】</span>
</div>
<div class="bd"></div>
</div>
<script src="common.js"></script>
<script>
// 获取元素
var box = my$("d_box");
var drop = my$("drop");
var close = my$("box_close");
// 给 drop 添加鼠标按下事件，在内部继续绑定一个鼠标移动事件
drop.onmousedown = function (e){
e = e || window.event;
// 记录鼠标按下的时候，鼠标在父盒子内部的间距
var l = e.pageX - box.offsetLeft;
var t = e.pageY - box.offsetTop;
// 鼠标移动事件
drop.onmousemove = function(e){
e = e || window.event;
// 鼠标移动过程中，可以计算box的left和top
var newLeft = e.pageX - l;
var newTop = e.pageY - t;
// 赋值给box的样式属性
box.style.left = newLeft + "px";
box.style.top = newTop + "px";
};
};
drop.onmouseup = function(){
drop.onmousemove = null;
};
close.onclick = function(){
box.style.display = "none";
};
</script>
</body>
</html>
弹出登录窗口
<!DOCTYPE html>
<html>
<head lang="en">
<meta charset="UTF-8">
<title></title>
<style>
.login-header {
width: 100%;
text-align: center;
height: 30px;
font-size: 24px;
line-height: 30px;
}
ul, li, ol, dl, dt, dd, div, p, span, h1, h2, h3, h4, h5, h6, a {
padding: 0px;
margin: 0px;
}
.login {
width: 512px;
position: absolute;
border: #ebebeb solid 1px;
height: 280px;
left: 50%;
right: 50%;
background: #ffffff;
box-shadow: 0px 0px 20px #ddd;
z-index: 9999;
margin-left: -256px;
margin-top: 140px;
display: none;
}
.login-title {
width: 100%;
margin: 10px 0px 0px 0px;
text-align: center;
line-height: 40px;
height: 40px;
font-size: 18px;
position: relative;
cursor: move;
-moz-user-select:none;/*火狐*/
-webkit-user-select:none;/*webkit浏览器*/
-ms-user-select:none;/*IE10*/
-khtml-user-select:none;/*早期浏览器*/
user-select:none;
}
.login-input-content {
margin-top: 20px;
}
.login-button {
width: 50%;
margin: 30px auto 0px auto;
line-height: 40px;
font-size: 14px;
border: #ebebeb 1px solid;
text-align: center;
}
.login-bg {
width: 100%;
height: 100%;
position: fixed;
top: 0px;
left: 0px;
background: #000000;
filter: alpha(opacity=30);
-moz-opacity: 0.3;
-khtml-opacity: 0.3;
opacity: 0.3;
display: none;
}
a {
text-decoration: none;
color: #000000;
}
.login-button a {
display: block;
}
.login-input input.list-input {
float: left;
line-height: 35px;
height: 35px;
width: 350px;
border: #ebebeb 1px solid;
text-indent: 5px;
}
.login-input {
overflow: hidden;
margin: 0px 0px 20px 0px;
}
.login-input label {
float: left;
width: 90px;
padding-right: 10px;
text-align: right;
line-height: 35px;
height: 35px;
font-size: 14px;
}
.login-title span {
position: absolute;
font-size: 12px;
right: -20px;
top: -30px;
background: #ffffff;
border: #ebebeb solid 1px;
width: 40px;
height: 40px;
border-radius: 20px;
}
</style>
</head>
<body>
<div class="login-header"><a id="link" href="javascript:void(0);">点击，弹出登录框</a></div>
<div id="login" class="login" >
<div id="title" class="login-title">登录会员
<span><a id="closeBtn" href="javascript:void(0);" class="close-login">关闭</a></span>
</div>
<div class="login-input-content">
<div class="login-input">
<label>用户名：</label>
<input type="text" placeholder="请输入用户名" name="info[username]" id="username" class="list-input">
</div>
<div class="login-input">
<label>登录密码：</label>
<input type="password" placeholder="请输入登录密码" name="info[password]" id="password" class="list-input">
</div>
</div>
<div id="loginBtn" class="login-button"><a href="javascript:void(0);" id="login-button-submit">登录会员</a></div>
</div>
<!-- 遮盖层 -->
<div id="bg" class="login-bg" ></div>
<script>
// 获取元素
var link = document.getElementById("link");
var login = document.getElementById("login");
var bg = document.getElementById("bg");
var closeBtn = document.getElementById("closeBtn");
// 添加 link 的点击事件，让登录窗口和遮盖层显示
link.onclick = function () {
login.style.display = "block";
bg.style.display = "block";
};
// 添加 btn 的点击事件，让登录窗口和遮盖层隐藏
closeBtn.onclick = function () {
login.style.display = "none";
bg.style.display = "none";
};
</script>
</body>
</html>
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