How do I get the text from a textbox into a variable that is being sent through an AJAX 'POST' request? – Jquery ajax

I want the text from the ‘txtDATE’ textbox into the variable press_date.
The current AJAX post is working perfectly. (except that it’s static and I want the variable).
I have been searching for answers and trying everything all day. Any help is appreciated.

<td>
     <asp:TextBox ID="txtDATE" runat="server" AutoPostBack="true" Width="75px" ></asp:TextBox>
</td>

var press = "'1000'";
var press_date = "'2020-08-01'";
$.ajax({
 type: "POST",
 url: "1000TIOT.aspx/GetChartData",
 data: "{ press: " + press +  ", press_date: " + press_date + " }",
 contentType: "application/json; charset=utf-8",
 dataType: "json",
 success: function (r) {
     var data1 = google.visualization.arrayToDataTable(r.d);
     var chart = new google.visualization.BarChart($("#chart")[0]);
     chart.draw(data1, options);
 },
 failure: function (r) {
     alert(r.d);
 },
 error: function (r) {
     alert(r.d);
 }
});