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HTML

CSS

CSS Base

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JavaScript

Babel includes JSX processing.

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Packages

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HTML

              
                <div class="box">
  <h2>data-contentを指定して色変更</h2>
  <p>文章が複数あるなかの</p>
  <p data-content="重要">重要なところだけ</p>
  <p>色を変えたい</p>
</div>
<div class="box">
  <h2>href属性を指定してfont-size変更</h2>
  <p>link3だけ大きくする</p>
  <a href="#">リンク1へ</a>
  <a href="#">リンク2へ</a>
  <a href="link3">リンク3へ</a>
</div>

<div class="box">
  <h2>JSでも大活躍</h2>
  <p data-content="toBig">文字が大きくなるボタン</p>
  <button id="clickFn">大きくする</button>
</div>
              
            
!

CSS

              
                .box{
  padding:10px;
  border:1px solid #f2f2f2;
  margin-bottom:10px;
}

button{
  border:none;
  background:#0046cc;
  padding:10px 20px;
  color:#fff;
  border-radius:5px;
}

a[href="link3"]{
  font-size:26px;
}

p[data-content="重要"]{
  color:red;
}
              
            
!

JS

              
                
document.getElementById("clickFn").onclick = function() {
  let targetElm = document.querySelector('p[data-content="toBig"]');
  targetElm.style.fontSize="30px";
};
              
            
!
999px

Console