{{ $imgSrc := $image.RelPermalink }}
{{ $imgWidth := $image.Width }}
{{ $imgHeight := $image.Height }}
<img src="{{ $imgSrc }}" data-size="{{ printf "%dx%d" $imgWidth $imgHeight }}"/>

<!-- Root element of PhotoSwipe. Must have class pswp. -->
<div class="pswp" tabindex="-1" role="dialog" aria-hidden="true">
    <!-- Background of PhotoSwipe. 
         It's a separate element as animating opacity is faster than rgba(). -->
    <div class="pswp__bg"></div>

    <!-- Slides wrapper with overflow:hidden. -->
    <div class="pswp__scroll-wrap">

        <!-- Container that holds slides. 
            PhotoSwipe keeps only 3 of them in the DOM to save memory.
            Don't modify these 3 pswp__item elements, data is added later on. -->
        <div class="pswp__container">
            <div class="pswp__item"></div>
            <div class="pswp__item"></div>
            <div class="pswp__item"></div>
        </div>

        <!-- Default (PhotoSwipeUI_Default) interface on top of sliding area. Can be changed. -->
        <div class="pswp__ui pswp__ui--hidden">

            <div class="pswp__top-bar">

                <!--  Controls are self-explanatory. Order can be changed. -->
                <div class="pswp__counter"></div>
                <button class="pswp__button pswp__button--close" title="Close (Esc)"></button>
                <button class="pswp__button pswp__button--share" title="Share"></button>
                <button class="pswp__button pswp__button--fs" title="Toggle fullscreen"></button>
                <button class="pswp__button pswp__button--zoom" title="Zoom in/out"></button>

                <!-- Preloader demo https://codepen.io/dimsemenov/pen/yyBWoR -->
                <!-- element will get class pswp__preloader--active when preloader is running -->
                <div class="pswp__preloader">
                    <div class="pswp__preloader__icn">
                      <div class="pswp__preloader__cut">
                        <div class="pswp__preloader__donut"></div>
                      </div>
                    </div>
                </div>
            </div>

            <div class="pswp__share-modal pswp__share-modal--hidden pswp__single-tap">
                <div class="pswp__share-tooltip"></div> 
            </div>

            <button class="pswp__button pswp__button--arrow--left" title="Previous (arrow left)">
            </button>

            <button class="pswp__button pswp__button--arrow--right" title="Next (arrow right)">
            </button>

            <div class="pswp__caption">
                <div class="pswp__caption__center"></div>
            </div>
        </div>
    </div>
</div>

{{ define "main" }}
 :
 略
{{ partial "photoswipe.html" . }}
{{ end }}

import 'photoswipe/dist/photoswipe.css'
import 'photoswipe/dist/default-skin/default-skin.css'

import PhotoSwipe from 'photoswipe/dist/photoswipe.min.js'
import PhotoSwipeUI_Default from 'photoswipe/dist/photoswipe-ui-default.min.js'

const setup = () => {
  // 画像リストを作成
  const items = Array.from(document.querySelectorAll('img[data-size]')).map(i => {
    const wh = i.getAttribute('data-size').split('x')
    return {
      src: i.getAttribute('src'),
      w: parseInt(wh[0], 10),
      h: parseInt(wh[1], 10)
    }
  })
  // photoswipe.htmlで定義したルート
  const pswpElement = document.querySelector('.pswp')
  // 画像クリック時にギャラリーが表示されるようにする
  document.querySelectorAll('img[data-size]').forEach((e, i) => {
    e.onclick = () => {
      const gallery = new PhotoSwipe(pswpElement, PhotoSwipeUI_Default, items, {
        shareEl: false,
        index: i
      })
      gallery.init()
    }
  })
}
setup()

:
略

{{ $scripts := resources.Get "output/js/pswp.js" | fingerprint }}
{{ with $scripts }}
  <script type="text/javascript">
    document.querySelectorAll('img[data-size]').forEach(img => {
      img.style.cursor = 'pointer'
      img.onclick = (event) => {
        // 初回クリックでモジュールをダウンロード
        import("{{ .Permalink | relURL }}").then(() => {
          // ダウンロード完了後改めてクリック
          event.target.click()
        })
      }
      //-> このonclickはpswp.jsロード後に上書きされる
    })
  </script>
{{end}}