一、表单
1、this指事件的调用者
2、input.value 表单更换内容
3、innerHTML更换盒子里的内容，文字、标签都能换。
4、isNaN("12")如果里面的不是个数字，返回true
二、表单自动获得焦点
txt.focus();//方法
Onfocus事件
三、鼠标经过选择表单
select();选择
txt.onmouseover=function(){
this.select();
}
四、获取某类元素
getElementById();//获取一个标签元素
getElementsByTagName(“li”);//获取多个标签，伪数组
lis[0],lis[i]
五、placeholder表单占位符
<input type="text" id="txt" placeholder="必败的国际品牌">
案例：
1、仿淘宝搜索框
<!doctype html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>仿淘宝搜索框</title>
<style>
.search{
width: 400px;
height: 30px;
margin: 100px auto;
position: relative;
}
.search input{
width: 300px;
height: 25px;
float: left;
}
.search label{
position: absolute;
left: 15px;
top:5px;
color: #c1c1c1;
cursor: text;
}
.search button{
display: block;
width: 50px;
height: 33px;
background-color: orange;
color: #fff;
text-decoration: none;
border: 1px solid #f1f1f1;
float: left;
position: absolute;
top:-1px;
left: 303px;
font-size: 16px;
cursor: pointer; }
</style>
<script>
window.onload=function(){
function $(id){return document.getElementById(id);}
$("txt").oninput=function(){
if(this.value==""){
$("message").style.display="block";
}else{
$("message").style.display="none";
}
}
}
</script>
</head>
<body>
<div class="search">
<input type="text" id="txt">
<label for="txt" id="message">国际品牌</label>
<!--<input type="text" id="txt" placeholder="必败的国际品牌">-->
<button id="btn">搜索</button>
</div>
</body>
</html> 运行效果：
2、隔行变色
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>隔行变色</title>
</head>
<style>
.box{
width: 500px;
margin: 100px auto;
}
li{
list-style: none;
line-height: 30px;
}
li span{
margin-right:20px;
}
.current{
background-color: #c1c1c1!important;
}
</style>
<script>
window.onload=function(){
var lis=document.getElementsByTagName("li");
for(var i=0;i<lis.length;i++){
if(i%2==0){
lis[i].style.backgroundColor="#eee";
}
lis[i].onmouseover=function(){
this.className="current";//一定要用this
}
lis[i].onmouseout=function(){
this.className="";//一定要用this
}
} }
</script>
<body>
<div class="box">
<ul>
<li>
<span>上证指数</span><span>3641</span><span>10-5</span><span>0.16%</span>
</li>
<li>
<span>上证指数</span><span>3641</span><span>10-5</span><span>0.16%</span>
</li>
<li>
<span>上证指数</span><span>3641</span><span>10-5</span><span>0.16%</span>
</li>
<li>
<span>上证指数</span><span>3641</span><span>10-5</span><span>0.16%</span>
</li>
<li>
<span>上证指数</span><span>3641</span><span>10-5</span><span>0.16%</span>
</li>
<li>
<span>上证指数</span><span>3641</span><span>10-5</span><span>0.16%</span>
</li>
<li>
<span>上证指数</span><span>3641</span><span>10-5</span><span>0.16%</span>
</li>
<li>
<span>上证指数</span><span>3641</span><span>10-5</span><span>0.16%</span>
</li>
</ul>
</div>
</body>
</html> 运行效果：
3、数组声明与遍历
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>数组声明与遍历</title>
</head>
<script>
var num=10;
var arr=[1,3,5,7,9];//声明数组
var arr=new Array(1,3,5);
var textArr=["刘备","诸葛亮","项羽","张飞","赵云"];
console.log(textArr[1]);//使用数组
console.log(textArr.length)//求数组长度
//遍历数组一
for(var i=0;i<textArr.length;i++){
console.log(textArr[i]);
}
//遍历数组二（推荐）
for(var i= 0,len=textArr.length;i<len;i++){
console.log(textArr[i]);
}
</script>
<body>
</body>
</html>
4、获取某类元素
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Title</title>
<script>
window.onload=function(){
//获取某类元素
/*var lis=document.getElementsByTagName('li');
//lis[0].innerHTML="abc";
for(var i=0;i<lis.length;i++){
lis[i].innerHTML="abc";
}*/ //金字塔打印
/*function line(){
17 for(var i=1;i<100;i++){
18 document.write("<hr width="+i+"%/>");
19 }
20 }
21 line();*/ //自动获取焦点
/*var txt=document.getElementById("txt");
txt.focus();//focus()自动获取焦点的方法*/ //自动选择表单内容
/* var txt=document.getElementById("txt");
txt.onmouseover=function(){
this.select();
}*/
}
</script>
</head>
<body>
<!-- <div id="box">
<ul>
<li>1234567890</li>
<li>1234567890</li>
<li>1234567890</li>
<li>1234567890</li>
<li>1234567890</li>
</ul>
</div>-->
<input type="text" id="txt" value="请输入内容">
<button>搜索</button>
</body>
</html>