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HTML

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HTML preprocessors can make writing HTML more powerful or convenient. For instance, Markdown is designed to be easier to write and read for text documents and you could write a loop in Pug.

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About the <head>

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Insecure Resource

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CSS

About CSS Preprocessors

CSS preprocessors help make authoring CSS easier. All of them offer things like variables and mixins to provide convenient abstractions.

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CSS Base

About CSS Base

It's a common practice to apply CSS to a page that styles elements such that they are consistent across all browsers. We offer two of the most popular choices: normalize.css and a reset. Or, choose Neither and nothing will be applied.

Vendor Prefixing

About Vendor Prefixing

To get the best cross-browser support, it is a common practice to apply vendor prefixes to CSS properties and values that require them to work. For instance -webkit- or -moz-.

We offer two popular choices: Autoprefixer (which processes your CSS server-side) and -prefix-free (which applies prefixes via a script, client-side).

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JavaScript

About JavaScript Preprocessors

JavaScript preprocessors can help make authoring JavaScript easier and more convenient.

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Babel includes JSX processing.

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Packages

Add Packages

Search for and use JavaScript packages from npm here. By selecting a package, an import statement will be added to the top of the JavaScript editor for this package.

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Using packages here is powered by esm.sh, which makes packages from npm not only available on a CDN, but prepares them for native JavaScript ESM usage.

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HTML 

              
                <!-- スライダーのコンテナ -->
<div class="swiper">
  <!-- 必要に応じたwrapper -->
  <div class="swiper-wrapper">
    <!-- スライド -->
    <div class="swiper-slide">Slide 1</div>
    <div class="swiper-slide">Slide 2</div>
    <div class="swiper-slide">Slide 3</div>
  </div>
  <div class="swiper-button-next"></div>
  <div class="swiper-button-prev"></div>
</div>

<p>現在の表示されてるスライド：<span>1</span></p>
!

CSS 

              
                .swiper--wrapper {
  /* wrapperのサイズを調整 */
  width: 100%;
  height: 100px;
}

.swiper-slide {
  /* スライドのサイズを調整、中身のテキスト配置調整、背景色 */
  color: #ffffff;
  width: 100%;
  height: 100%;
  text-align: center;
  line-height: 100px;
}

.swiper-slide:nth-child(3n + 1) {
  /*1、4、7、3n+1枚目の背景色 */
  background-color: #de4439;
}

.swiper-slide:nth-child(3n + 2) {
  /*2、5、8、3n+2枚目の背景色 */
  background-color: #fcd500;
}

.swiper-slide:nth-child(3n + 3) {
  /*3、6、9、3n+3枚目の背景色 */
  background-color: #53c638;
}
!

JS 

              
                const swiper = new Swiper(".swiper", {
    navigation: {
      nextEl: ".swiper-button-next",
      prevEl: ".swiper-button-prev",
    },
    on: {
    // スライドの切り替わりアニメーションが終了した時に実行
      slideChangeTransitionEnd: function() {
        const swiperPageNum = document.querySelector('p span');
        swiperPageNum.textContent = this.realIndex + 1;
      },
    }
});
!
999px

Console