要检查表行是否存在，请使用is()带有：visible选择器的方法-
if($(".row").is(":visible")) {
alert("Visible!");
}您可以尝试运行以下代码，以了解如何检查是否存在行。它甚至在创建新行时通知-
<!DOCTYPE html>
<html>
<head>
<title>jQuery - Add Table Rows</title>
<style>
table{
width: 100%;
margin: 25px 0;
border-collapse: collapse;
}
table, th, td{
border: 1px solid #6C220B;
}
table th, table td{
padding: 8px;
text-align: left;
}
</style>
<script src="https://code.jquery.com/jquery-3.2.1.min.js"></script>
<script>
$(document).ready(function(){
$(".row").click(function(){
if($(".row").is(":visible")) {
alert("Exists: A new row will create now.");
}
var name = $("#name").val();
var subject = $("#subject").val();
var markup = "<tr><td><input type='checkbox' name='record'></td><td>" + name + "</td><td>" + subject + "</td></tr>";
$("table tbody").append(markup);
});
});
</script>
</head>
<body>
<form>
<input type="text" id="name" placeholder="Enter Name">
<input type="text" id="subject" placeholder="Enter Subject">
<input type="button" class="row" value="Click to Add Row">
</form>
<table>
<thead>
<tr>
<th>Choose</th>
<th>Name</th>
<th>Subject</th>
</tr>
</thead>
<tbody>
<tr>
<td><input type="checkbox" name="result"></td>
<td>Amit</td>
<td>Java</td>
</tr>
</tbody>
</table>
</body>
</html>