old_contents: 
  $(document).ready(function() {
  
      $("#show-modify-form").click(function () {
          $("#table-view").toggle();
          $(".form-view").toggle();
          $("#date-validation").text("");
  
          var text = $("#show-modify-form").text();
          var new_text = (text.trim() == "Edit") ? "Hide form" : "Edit";
          $("#show-modify-form").text(new_text);
      });
  
      $("#embargo-update-form").submit(function (event) {
          event.preventDefault();
          $('#update-embargo-modal').modal('show');
      });
  
      $("#embargo-update-modal").submit(function (event) {
          var data = $('#embargo-update-form').serialize();
          data["validation_only"]="False";
          $.ajax({
              url: window.templateVars.updateEmbargoUrl,
              type: "post",
              data: data,
              success: function (response) {
                  location.reload();
              }
          }).fail(function (jqXHR, textStatus, error) {
              $("#date-validation").text(jqXHR.responseText);
          });
      });
  
      $("#datepicker").datepicker({
          format: "mm/dd/yyyy",
          startDate: "+0d"
      })
          .on("change", function (e) {
              $("#embargo-update-submit").removeClass('disabled');
              $("#date-validation").text('');
              var data = $('#embargo-update-form').serialize();
              data["validation_only"]="True";
              $.ajax({
                  url: window.templateVars.updateEmbargoUrl,
                  type: "post",
                  data: data
              }).fail(function (jqXHR, textStatus, error) {
                  $("#date-validation").text(jqXHR.responseText);
                  $("#embargo-update-submit").addClass('disabled');
              });
          });
  });
  
new_contents: 
  $(document).ready(function() {
  
      $("#show-modify-form").click(function () {
          $("#table-view").toggle();
          $(".form-view").toggle();
          $("#date-validation").text("");
  
          var text = $("#show-modify-form").text();
          var new_text = (text.trim() == "Edit") ? "Hide form" : "Edit";
          $("#show-modify-form").text(new_text);
      });
  
      $("#embargo-update-form").submit(function (event) {
          event.preventDefault();
          $('#update-embargo-modal').modal('show');
      });
  
      $("#embargo-update-modal").submit(function (event) {
          var data = $('#embargo-update-form').serialize();
          data["validation_only"]="False";
          $.ajax({
              url: window.templateVars.updateEmbargoUrl,
              type: "post",
              data: data,
              success: function (response) {
                  location.reload();
              }
          }).fail(function (jqXHR, textStatus, error) {
              $("#date-validation").text(jqXHR.responseText);
          });
      });
  
      $("#datepicker").datepicker({
          format: "mm/dd/yyyy",
          startDate: "+0d"
      })
          .on("change", function (e) {
              $("#embargo-update-submit").prop('disabled', false);
              $("#date-validation").text('');
              var data = $('#embargo-update-form').serialize();
              data["validation_only"]="True";
              $.ajax({
                  url: window.templateVars.updateEmbargoUrl,
                  type: "post",
                  data: data
              }).fail(function (jqXHR, textStatus, error) {
                  $("#date-validation").text(jqXHR.responseText);
                  $("#embargo-update-submit").prop('disabled', true);
              });
          });
  });
  
subject: Add disabled prop instead of just class