http://blog.csdn.net/zyxlinux888/article/details/7391240
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定义和用法
focus() 方法用于在密码域上设置焦点。
语法
passwordObject.focus()
实例
下面的例子可设置或移开密码域上的焦点：
<html>
<head>
<script type="text/javascript">
function setFocus()
{
document.getElementById('password1').focus()
}
function loseFocus()
{
document.getElementById('password1').blur()
}
</script>
</head>
<body>
<form>
<input type="password" id="password1" value="thgrt456" />
<input type="button" onclick="setFocus()" value="Set focus" />
<input type="button" onclick="loseFocus()" value="Lose focus" />
</form>
</body>
</html>
实例2：<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=gb2312" />
<title>Untitled Document</title>
<script type="text/javascript">
?????? function chg(){
??? ?? document.getElementById("setfocus").value="";
?????? }
??? ?? function newChg(){
??? ?? document.getElementById("setfocus").value="请输入关键字";
?????? }
</script>
</head>
<body>
<input type="text" name="name" size="15" class="input" id="setfocus" value="请输入关键字" onfocus="chg()" onblur="newChg()">
</body>
</html>
实例3
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=gb2312" />
<title>Untitled Document</title>
<script type="text/javascript">
function $(ID) {return document.getElementById(ID);}
function chg(){
$("setfocus").value="";
}
function newChg(){
??? if($("setfocus").value==""){
??? ??? $("setfocus").value="请输入关键字";
??? ??? }
??? else{return $("setfocus").value }
}
</script>
</head>
<body>
<input type="text" name="name" size="15" class="input" id="setfocus" value="请输入关键字" onfocus="chg()" onblur="newChg()">
</body>
</html>