Ajax overwriting existing String in Table

I have a<table> i can click on a <td> and a Dialog shows up.Now i can enter an String and submit it.The submit writes the String into my Database and displays it on the <td>Element.

What i want to do, is that if i click again on the same <td>-Element and i enter a different Text, this should overwrite the old Text in the Database and `.

What i am looking for is how to get that working with Ajax.`

$(document).ready(function() {
    var activeTD;
    $(".td_test").click(function() {
        $("#bModal").modal('show');
        activeTD = this;
        if ($(activeTD).html()) {
            // The cell has stuff in it
            $("input[name=getdata]").val($(activeTD).html());
        }
        else {
            // The cell is empty
              $("input[name=getdata]").val("");
        }
    }); 
    $("#ajaxtest").submit(function(ev) {
        var name = $("#ajaxtest").serialize();
        ev.preventDefault();
        $.ajax({
            type:"POST",
            processData:false,
            url:"InsertServlet",
            dataType: "text",
            data: name
        })
        .done(function(data){

            $(activeTD).text(data);
        });
        $("#bModal").modal('hide');
    });
    $("input[name=deleteData]").click(function(e){
        var name = $("#ajaxtest").serialize();
        e.preventDefault();
        $.ajax({
            type:"POST",
            processData:false,
            datatype:"text",
            url:"DeleteServlet",
            data:name
        })
        .done(function(data){
            $(activeTD).text("");   
        });
        $("#bModal").modal('hide');
    });
});

This is what i have so far, a working DELETE und SUBMIT button. Hope someone can help :)