js如何判断注册表单的关联。
比如先选择下拉框,如果下拉框的值为2,那么就必须选择下面的文本框,才能提交数据。。<select name="title"><option>选择</option><option value="1">1</option><option value="2">2</option><option value="3">3</option></select><input name="author" type="text">比如是上面这样子的,如何写js代码
比如先选择下拉框,如果下拉框的值为2,那么就必须选择下面的文本框,才能提交数据。。<select name="title"><option>选择</option><option value="1">1</option><option value="2">2</option><option value="3">3</option></select><input name="author" type="text">比如是上面这样子的,如何写js代码
<select name="title" onchange="changeValue()"><option>选择</option><option value="1">1</option><option value="2">2</option><option value="3">3</option></select><input name="author" onchange="changeSubmit()" type="text">
<input type="submit" name="submit" value="提交" />
<script>
function changeValue(){
if(document.getElementsByName("title")[0].value=="2")
{
document.getElementsByName("author")[0].focus();
document.getElementsByName("submit")[0].disabled="false";
}
}
function changeSubmit()
{
if(document.getElementsByName("author")[0].value!="")
{
document.getElementsByName("submit")[0].disabled="";
}else
{
changeValue();
}
}
</script>
<select id="sel" onchange="fn(this);">
<option value="1">1</option>
<option value="2">2</option>
<option value="3">3</option>
</select>
<input type="text" id="it" name="xxx" style="display:none"/><input type="submit" value="提交" onclick="sub();"/><script type="text/javascript">
var fn = function(box){
if(box.value==2)
document.getElementById('it').style.display="";
else document.getElementById('it').style.display="none"; }; var sub=function(){
var v =document.getElementById('sel').value;
if(v==2&&document.getElementById('it').value=='') alert('请填写输入框内容');
else alert('提交'); }</script>
{
if(document.getElementsByName("title")[0].value=="2"&&document.getElementsByName("author")[0].value=="")
{
alert("因为你在下拉列表中选择了2,所以,下面的文本框中你必须填入内容");
return false;
}else
{
return true;
}
}在你的 form 里面 添加 onsubmit="return toSubmit()";
<head>
<title></title>
<script type="text/javascript">
function check()
{
var val = document.getElementById('title').value;
if(val == 2){
var author = document.getElementById('author').value;
if(!author){
alert('请输入author');
return false;
}
}
} </script>
</head>
<body> <form onsubmit="return check();" action="" method="post"> <select name="title" id="title">
<option>
选择
</option>
<option value="1">
1
</option>
<option value="2">
2
</option>
<option value="3">
3
</option>
</select> <input name="author" type="text" id="author">
<input type="submit" value="提交"> </form>
</body>
</html>