<!doctype html>
<html>
<head>
<meta charset="utf-8">
<title>placeholder 效果的实现</title>
<script src="http://code.jquery.com/jquery-1.10.1.min.js"></script>
</head>
<style>
body {
font-size: 12px;
}
div {
position: relative;
}
.userName-group,
.pswd-group{
width: 153px;
height: 24px;
margin-bottom:10px;
}
label{
margin-left:3px;
line-height: 24px;
z-index: 1;
color: #999;
}
.userName-group input,
.pswd-group input{
position: absolute;
top: 0;
left:0;
width: 153px;
height:22px;
border:1px solid #bbb;
z-index: 999;
background-color: transparent;
}
</style>
<body>
<h1>placeholder 效果</h1>
<input type="text" placeholder="用户名">
<input type="password" placeholder="密码">
<h1>placeholder 效果的实现</h1>
<div class="userName-group">
<label for="username">用户名</label>
<input type="text" id="username">
</div>
<div class="pswd-group">
<label for="password">密码</label>
<input type="password" id="password">
</div>
<script>
/*$(function(){
var input=$("input"),
len=input.length;
for(var i=0;i<len;i++){//判断浏览器是否记住信息
var val=input.eq(i).val();
if(val!==''){
input.eq(i).prev('label').hide();
}
}
$("label").click(function(){
$(this).next().focus();
})
$("#username,#password").keydown(function(){
$(this).prev().hide();
}).blur(function(){
var _this=$(this);
if (_this.val() == ''){
_this.prev().show();
}
});
})*/
//判断浏览器
var Sys = {};
var ua = navigator.userAgent.toLowerCase();
if (window.ActiveXObject){
Sys.ie = ua.match(/msie ([\d.]+)/)[1];
}
//else if (document.getBoxObjectFor){
// Sys.firefox = ua.match(/firefox\/([\d.]+)/)[1];
//}else if (window.MessageEvent && !document.getBoxObjectFor){
// Sys.chrome = ua.match(/chrome\/([\d.]+)/)[1];
//}else if (window.opera){
// Sys.opera = ua.match(/opera.([\d.]+)/)[1];
//}else if (window.openDatabase){
// Sys.safari = ua.match(/version\/([\d.]+)/)[1];
//}
window.onload=function(){
var input=document.getElementsByTagName('input'),
label=document.getElementsByTagName('label'),
username=document.getElementById('username'),
pwd=document.getElementById('password'),
len=input.length;
for(var i=0;i<len;i++){
var val=input.item(i).value,
div=input.item(i).parentNode;
if(val!==''){
label_s_h(div,'none');
}
}
label.onclick=function(){
this.nextSibling('input').focus;
}
username.onkeydown=pwd.onkeydown=function(){
var div=this.parentNode;
label_s_h(div,'none');
}
username.onblur=pwd.onblur=function(){
var _this=this,
div=this.parentNode,
val=_this.value;
if(val==''){
label_s_h(div,'block');
}
}
}
s=Sys.ie||'';//没有空s为undefined
function label_s_h(o,d){
/*if(s=='6.0'||s=='7.0'||s=='8.0'){
//s.indexOf('6'||'7'||'8')>0不知道为什么这样不对 ？？
//s=='6.0'||'7.0'||'8.0' 写在label_s_h()函数里判断就出错，chrome下也执行到这里，不写在函数里是对的
o.firstChild.style.display=d;//不知道为什么不能用.previousSibling ？？
}else{
o.childNodes[1].style.display=d;//不知道为什么ie9以上和chrome不支持firstChild ？？？
}*/
s=='6.0'||s=='7.0'||s=='8.0'?o.firstChild.style.display=d:o.childNodes[1].style.display=d;
}
</script>
</body>
</html>
