$('#myDiv').text()
Although you'd be better off doing something like:
var txt = $('#myDiv p').text();_x000D_
alert(txt);
_x000D_
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>_x000D_
<div id="myDiv"><p>Some Text</p></div>
_x000D_
Make sure you're linking to your jQuery file too :)