<script> function Changesel(){ var traget=document.getElementById("A1"); if (document.frm.lx.value=="GE"){ traget.style.display=""; }else{ traget.style.display="none"; } } </script> <form name="frm" id="frm"> <select name="lx" onChange="Changesel()"> <option value="GE">user</option> <option value="QT">pwd</option> </select> <input name="A1" type="text" > </form>
var str=document.getElementById("id").options; var value=str[document.getElementById("id").selectedIndex].text; var txt=document.createElement("input"); txt.setAttribute("type","text"); if(value=="账号"){ txt.setAttribute("maxlength","20"); } else{......,"10"} document.body.insertBefore(txt,document.getElementById("button"));
提示信息:<selectid='s1' onchange='setLength()'> <optionvalue='10'>密码 </option> <optionvalue='20'>账号 </option> </select> <input id='tbContent' type='text'><span id="SPANMsg"></span> var DDLOp=document.getElementById('s1'); var SPANMsg=document.getElementById('SPANMsg'); function setLength() { s1value=document.getElementById('s1').value; document.getElementById('t1').maxLegnth = s1value; if(s1value=='10'){msg="<font color=red>密码长度为10</font>";} else{msg="<font color=red>帐号长度为20</font>";} SPANMsg.innerHTML=msg; }
<select id='s1' onchange='setLength()'>
<option value='10'>密码</option>
<option value='20'>账号</option>
</select>
<input id='t1' type='text'>function setLength()
{
document.getElementById('t1').maxLegnth = document.getElementById('s1').value;
}
function Changesel(){
var traget=document.getElementById("A1");
if (document.frm.lx.value=="GE"){
traget.style.display="";
}else{
traget.style.display="none";
}
}
</script>
<form name="frm" id="frm">
<select name="lx" onChange="Changesel()">
<option value="GE">user</option>
<option value="QT">pwd</option>
</select>
<input name="A1" type="text" >
</form>
var value=str[document.getElementById("id").selectedIndex].text;
var txt=document.createElement("input");
txt.setAttribute("type","text");
if(value=="账号"){
txt.setAttribute("maxlength","20");
}
else{......,"10"}
document.body.insertBefore(txt,document.getElementById("button"));
<optionvalue='10'>密码 </option>
<optionvalue='20'>账号 </option>
</select>
<input id='tbContent' type='text'><span id="SPANMsg"></span>
var DDLOp=document.getElementById('s1');
var SPANMsg=document.getElementById('SPANMsg');
function setLength()
{
s1value=document.getElementById('s1').value;
document.getElementById('t1').maxLegnth = s1value;
if(s1value=='10'){msg="<font color=red>密码长度为10</font>";}
else{msg="<font color=red>帐号长度为20</font>";}
SPANMsg.innerHTML=msg;
}