输入字段为空时防止表单提交 [英] Preventing form submission when input field is empty
本文介绍了输入字段为空时防止表单提交的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！
问题描述
当未将任何值提供给roll输入字段时，empty()函数会产生警报，但此空值仍会传递给retrive.php.那么如何阻止这种情况的发生，仅在提供某些输入值时才将值传递给retrive.php?
When no value is provided to the roll input field an alert is produced by the empty() function but this empty value is still passed to retrive.php. So how can I stop this from happening and only pass the value to retrive.php when some input value is provided?
<html>
<head>
<title>STUDENT FORM</title>
<script type="text/javascript">
function empty()
{
var x;
x = document.getElementById("roll-input").value;
if (x == "")
{
alert("Enter a Valid Roll Number");
};
}
</script>
</head>
<body >
<h1 align="center">student details</h1>
<div id="input">
<form action='retrive.php' method='get'>
<fieldset>
<legend>Get Details</legend>
<dl>
<dt><label for="roll-input">Enter Roll Number</label></dt>
<dd><input type="text" name="roll" id="roll-input"><dd>
<input type="submit" value="submit" onClick="empty()" />
</dl>
</fieldset>
</form>
</div>
</body>
</html>
推荐答案
您需要返回false才能取消提交.
You need to return false to cancel the submit.
function empty() {
var x;
x = document.getElementById("roll-input").value;
if (x == "") {
alert("Enter a Valid Roll Number");
return false;
};
}
和
<input type="submit" value="submit" onClick="return empty()" />
jsFiddle example
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