Preview in upload file with javascript and ruby on rails

upload.html.erb

  <div class="control-group">
    <%= form.label :plan_image %>
    <div class="controls">
      <div id="plan_image_preview_block" class="imageUpload imageUpload-16_9" style="<%= 'display: none;'.html_safe if @plan.try(:plan_image).try(:url).nil? %>">
        <div class="imageUpload-media" id="plan_image_preview" style="background-image: url(<%= @plan.try(:plan_image).try(:url) || '' %>);"></div>
      </div>
      <div class="input-file-wrapper">
        <a class="btn btn--s btn--secondary">
          <% if @plan.plan_image.present? && @plan.plan_image.file.exists? %>
            <i class="icon icon-16 flaticon stroke photo-1"></i> Change image
          <% else %>
            <i class="icon icon-16 flaticon stroke upload-1"></i> Upload a file
          <% end %>
        </a>
         <%= form.file_field :plan_image %>
      </div>
      <p class="help-block">
        Resolution: 1280x720 &#8212; Aspect Ratio: 16:9
      </p>
    </div>
  </div>


<script>

  $(document).ready(function(){
    $('input[type="file"]').change(function(){
      var image = window.URL.createObjectURL(this.files[0]);
      $("#plan_image_preview").css("background-image", "url(" + image + ")");
      $("#plan_image_preview_block").show();
    });
  });

</script>