cssloaders_in_header.html

<style>
  .load1 .loader,
.load1 .loader:before,
.load1 .loader:after {
  background: #ffffff;
    -webkit-animation: load1 1s infinite ease-in-out;
  animation: load1 1s infinite ease-in-out;
  width: 1em;
  height: 4em;
}
.load1 .loader {
  color: #ffffff;
    text-indent: -9999em;
  margin: 88px auto;
  position: relative;
  font-size: 11px;
  -webkit-transform: translateZ(0);
  -ms-transform: translateZ(0);
  transform: translateZ(0);
  -webkit-animation-delay: -0.16s;
  animation-delay: -0.16s;
}
.load1 .loader:before,
.load1 .loader:after {
  position: absolute;
  top: 0;
  content: '';
}
.load1 .loader:before {
  left: -1.5em;
  -webkit-animation-delay: -0.32s;
  animation-delay: -0.32s;
}
.load1 .loader:after {
  left: 1.5em;
}
@-webkit-keyframes load1 {
  0%,
  80%,
  100% {
    box-shadow: 0 0;
    height: 4em;
  }
  40% {
    box-shadow: 0 -2em;
    height: 5em;
  }
}
@keyframes load1 {
  0%,
  80%,
  100% {
    box-shadow: 0 0;
    height: 4em;
  }
  40% {
    box-shadow: 0 -2em;
    height: 5em;
  }
}
.shiny-spinner-output-container {
  position: relative;
}

.load-container {
  position: absolute;
  top: 50%;
  -webkit-transform: translateY(-50%);
  transform: translateY(-50%);
  /* to avoid showing a vertical scrollbar
  http://stackoverflow.com/questions/38251204/horizontal-animation-causes-vertical-scrollbar-in-css */
    overflow:hidden; 
  width: 100%;
}

.shiny-spinner-hidden {
  position: absolute;
  top:0;
  left:0;
  z-index: -1;
  visibility:hidden;
}
.load1 .loader, .load1 .loader:before, .load1 .loader:after {background: #0275D8} .load1 .loader {color: #0275D8}
    .load1 .loader {font-size: 8px}
  </style>
    <script>
    (function() {
      var output_states = [];
      
      function show_spinner(id) {
        $("#"+id).siblings(".load-container, .shiny-spinner-placeholder").removeClass('shiny-spinner-hidden');
        $("#"+id).siblings(".load-container").siblings('.shiny-bound-output, .shiny-output-error').css('visibility', 'hidden');
        // if there is a proxy div, hide the previous output
        $("#"+id).siblings(".shiny-spinner-placeholder").siblings('.shiny-bound-output, .shiny-output-error').addClass('shiny-spinner-hidden');
      }
      
      function hide_spinner(id) {
        $("#"+id).siblings(".load-container, .shiny-spinner-placeholder").addClass('shiny-spinner-hidden');
        $("#"+id).siblings(".load-container").siblings('.shiny-bound-output').css('visibility', 'visible');
        // if there is a proxy div, show the previous output in case it was hidden
        $("#"+id).siblings(".shiny-spinner-placeholder").siblings('.shiny-bound-output').removeClass('shiny-spinner-hidden');
      }
      
      function update_spinner(id) {
        if (!(id in output_states)) {
          show_spinner(id);
        }
        if (output_states[id] <= 0) {
          show_spinner(id);
        } else {
          hide_spinner(id);
        }
      }
      
      $(document).on('shiny:bound', function(event){ 
        /* if not bound before, then set the value to 0 */
          if (!(event.target.id in output_states)) {
            output_states[event.target.id] = 0;
          }
        update_spinner(event.target.id);
      });
      
      /* When recalculating starts, show the spinner container & hide the output */
        $(document).on('shiny:outputinvalidated', function(event) {
          output_states[event.target.id] = 0;
          update_spinner(event.target.id);
        });
      
      /* When new value or error comes in, hide spinner container (if any) & show the output */
        $(document).on('shiny:value shiny:error', function(event) {
          output_states[event.target.id] = 1;
          update_spinner(event.target.id);
        });
    }());
  </script>