$('input#mybutton').click(function() {
var text = $('textarea#mytextarea').val();
//send to server and process response
});
<textarea></textarea>
<button id="btn">Check Textarea Value</button>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.5.1/jquery.min.js"></script>
<script>
$("#btn").click(function() {
var txtArea = $("textarea").val();
alert(txtArea); // alert the value of textarea
});
</script>
$("textarea").val()
var message = $('textarea#message').val();