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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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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-.

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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 

              
                <section>
  <h1>ガンダム大地に立つ</h1>
  <p>アムロは<span data-text="">ガンダム</span>のコクピットに飛び乗り、機器メーターを見て「こいつ、動くぞ！」と言った。</p>
</section>
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CSS 

              
                section {
  width: 100%;
  margin: 0 auto;
  max-width: 500px;
  padding: 20px;
  border: 1px solid #ccc;
  border-radius: 10px;
}

span {
  background: #eee;
  padding: 3px;
  position: relative;
}

span:hover {
   cursor: pointer; 
}
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JS 

              
                //DOM     
const span = document.querySelector("span");

span.addEventListener('click', function () {
  alert('ガンダム（GUNDAM）は、「ガンダムシリーズ」に登場する架空の兵器。有人操縦式の人型ロボット兵器「モビルスーツ」（MS）の一つ。初出は、1979年放送のテレビアニメ『機動戦士ガンダム』。作中の軍事勢力の一つ「地球連邦軍」が開発した試作機の1機で、主人公「アムロ・レイ」の搭乗機。額のV字型ブレードアンテナと、人間の目を模した複眼式のセンサーカメラが特徴で、ほかのMSに比べ人間に近い形状を持つ。これらの特徴は、以降のシリーズ作品に登場する「ガンダムタイプ」の基本となった。敵対勢力である「ジオン公国軍」のMSの多くを凌駕する性能を持ち、パイロットのアムロの成長と相まって「一年戦争」で伝説的な戦果を上げる。（※Wikipediaより）');
}, false);
!
999px

Console