weseek__growi/lib/views/modal/create_template.html

<div class="modal create-template" id="create-template">
  <div class="modal-dialog">
    <div class="modal-content">

      <div class="modal-header bg-primary">
        <button type="button" class="close" data-dismiss="modal" aria-hidden="true">&times;</button>
        <div class="modal-title">{{ t('template.modal_label.Create/Edit Template Page') }}</div>
      </div>
      <div class="modal-body">
        <div class="form-group">
          <label class="mb-4">{{ t('template.modal_label.Create template under', page.path ) }}</label>
          <div class="row">
            <div class="col-sm-6">
              <div class="panel panel-default panel-select-template">
                <div class="panel-heading">{{ t('template.children.label') }}</div>
                <div class="panel-body">
                  <p class="text-center"><code>_template</code></p>
                  <p class="help-block text-center"><small>{{ t('template.children.desc') }}</small></p>
                </div>
                <div class="panel-footer text-center">
                  <a href="{% if page.path.endsWith('/') %}{{ page.path }}{% else %}{{ page.path}}/{% endif %}_template#edit-form"
                      class="btn btn-sm btn-primary" id="template-button-children">
                    作成/編集
                  </a>
                </div>
              </div>
            </div>
            <div class="col-sm-6">
              <div class="panel panel-default panel-select-template">
                <div class="panel-heading">{{ t('template.decendants.label') }}</div>
                <div class="panel-body">
                  <p class="text-center"><code>__template</code></p>
                  <p class="help-block text-center"><small>{{ t('template.decendants.desc') }}</small></p>
                </div>
                <div class="panel-footer text-center">
                  <a href="{% if page.path.endsWith('/') %}{{ page.path }}{% else %}{{ page.path }}/{% endif %}__template#edit-form"
                      class="btn btn-sm btn-primary" id="template-button-decendants">
                    作成/編集
                  </a>
                </div>
              </div>
            </div>
          </div>
        </div>
      </div>
    </div><!-- /.modal-content -->
  </div><!-- /.modal-dialog -->
</div><!-- /.modal -->

<script>
  let pagePath = $('#link-to-template').attr('href');

  if (pagePath.endsWith('/')) {
      pagePath = pagePath.slice(0, -1);
  };

  $.get('/_api/pages.templates?path=' + pagePath)   // don't use template literal(`...${}`) for IE11
    .then(function(templateInfo) {                  // don't use arrow function for IE11
      const buttonTextChildren = templateInfo.childrenTemplateExists ? '{{ t("Edit") }}' : '{{ t("Create") }}';
      const buttonTextDecendants = templateInfo.decendantsTemplateExists ? '{{ t("Edit") }}' : '{{ t("Create") }}';

      $('#template-button-children').text(buttonTextChildren);
      $('#template-button-decendants').text(buttonTextDecendants);

      $('#template-type').on('change', function() {
        // enable button
        $('#link-to-template').removeClass('disabled');

        if ($('#template-type').val() === 'children') {
          href = pagePath + '/_template#edit-form';
          $('#link-to-template').attr('href', href);
          $('#create-template-button-link').text(buttonTextChildren);
        }
        else if ($('#template-type').val() === 'decentants') {
          href = pagePath + '/__template#edit-form';
          $('#link-to-template').attr("href", href);
          $('#create-template-button-link').text(buttonTextDecendants);
        };
      });
    });
</script>