How I can send data from Flask to JavaScript?

$("#id_of_btn").click(function () { // make ajax request on btn click
  $.ajax({
    type: "POST",
    url: "/mapaa", // url to the function
    data: {
      name: $("#id_of_input_tag").val(), // value of the form
    },
    success: function (response) {
      console.log(response); // response contains the json
    },
  });
});

data: $('form').serialize()