The regex to capture this is pretty simple, if you can guarantee that there are never nested tables. Nested tabled become much trickier to deal with.
/<table[^>]*class=("|')?.*?\bCLASSNAMEHERE\b.*?\1[^>]*>([\s\S]*?)</table>/im
For instance, if an attribute before class had a closing >
in it, which isn't likely, but possible, the regex would fall flat on it's face. Complex reges can try to prepare for that, but it's really not worth the effort.
However, jQuery all by itself can make this a breeze, if these elements are within the DOM. Regex can be easily fooled or tripped, deliberately or accidentally but that's why we have parsers. JQuery doesn't care what's nested or not within the element. It doesn't care about quote style, multiline, any of that.
$(document).ready(function () {
console.log($("table.myClassHere").prop("outerHTML"))
});
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.9.1/jquery.min.js"></script>
<table class="myClassHere">
<tr>
<td>Book Series</td>
</tr>
<tr>
<td>Pern</td>
</tr>
<tr>
<td>Hobbit</td>
</tr>
</table>
<table class="otherClassHere">
<tr>
<td>Movies</td>
</tr>
<tr>
<td>Avengers</td>
</tr>
<tr>
<td>Matrix</td>
</tr>
</table>