常用方法：
getElementsByName()- 根据name获取元素
getElementsByTagName() -获取元素
getAttribute() -获取元素属性
setAttribute() -设置元素属性
childNodes() -访问子节点
parentNode() -访问父节点
createElement() -创建元素节点
createTextNode() -创建文本节点
insertBefore() -插入节点
removeChild() -删除节点
offsetHeight -网页尺寸
scrollHeight -网页尺寸
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>测试</title>
</head>
<body>
<p name="pn">hello</p>
<p name="pn">hello</p>
<p name="pn">hello</p>
<p name="pn">hello</p>
<a id="aid" title="得到了a标签的属性">hello</a>
<a id="aid2">aid2</a>
<ul><li>1</li><li>2</li><li>3</li></ul>
<div id="div">
<p id="pid">pid</p>
</div>
<script>
//通过name和标签名获取元素
function getName(){
var count = document.getElementsByName("pn");
var count1=document.getElementsByTagName("p");
document.write("<hr>");
document.write("pn的长度是："+count.length);
document.write("<br>");
document.write("p的长度是："+count1.length);
var p =count[0];
var p1 =count[1];
p.innerHTML ="World";
p1.innerHTML="World";
}
getName();
//通过id获取元素，并获取元素的属性值
function getAttr(){
var anode = document.getElementById("aid");
var attr=anode.getAttribute("title");
document.write("<hr>");
document.write("属性title的值是："+attr);
}
getAttr();
function setAttr(){
var anode = document.getElementById("aid2");
anode.setAttribute("title","动态设置a的title属性");
var attr =anode.getAttribute("title");
document.write("<hr>");
document.write("设置之后的值是："+attr);
}
setAttr();
function getChildNode(){
var childnode=document.getElementsByTagName("ul")[0].childNodes;
document.write("<hr>");
document.write("childnode.length："+childnode.length);
}
getChildNode();
//创建元素
function createNode(){
var body = document.body;
var input = document.createElement("input");
input.type="button";
input.value="按钮";
body.appendChild(input);
}
createNode();
//添加节点
function addNode(){
var div = document.getElementById("div");
var node= document.getElementById("pid");
var newnode1=document.createElement("p");
var newnode2=document.createElement("hr");
newnode1.innerHTML = "动态添加第一个p元素";
div.insertBefore(newnode1,node);
div.insertBefore(newnode2,node);
}
addNode();
//移除节点
function removeNode(){
var div = document.getElementById("div");
var p=div.removeChild(div.childNodes[1]);
}
removeNode();
//获取文档宽度和长度
function getSize(){
var width = document.body.offsetWidth||document.documentElement.offsetWidth;
var height=document.body.offsetHeight;
document.write(width+","+height);
}
getSize();
</script>
</body>
</html>