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HTML

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CSS

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JavaScript

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Babel includes JSX processing.

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HTML 

              
                <h1>border-bottomで作るアンダーライン</h1>

<h2>色の変更(border-bottom-color)</h2>
<p>・指定なし<span class="code">(border-bottom-color: currentcolor;)</span></p><p class="example">テキストに<span class="under-line">アンダーライン</span>を引きます。</p>
<p>・色名で指定<span class="code">border-bottom-color: red;</span></p><p class="example">テキストに<span class="under-line color-name">アンダーライン</span>を引きます。</p>
<p>・カラーコードで指定<span class="code">border-bottom-color: #FF7403;</span></p><p class="example">テキストに<span class="under-line hex">アンダーライン</span>を引きます。</p>
<p>・rgbaで指定<span class="code">border-bottom-color: rgba(172, 54, 173, .5);</span></p><p class="example">テキストに<span class="under-line rgba">アンダーライン</span>を引きます。</p>

<h2>太さの変更(border-bottom-width)</h2>
<p>・指定なし<span class="code">(border-bottom-width: medium;)</span></p><p class="example">テキストに<span class="under-line">アンダーライン</span>を引きます。</p>
<p>・thinを指定<span class="code">border-bottom-width: thin;</span></p><p class="example">テキストに<span class="under-line thin">アンダーライン</span>を引きます。</p>
<p>・thickを指定<span class="code">border-bottom-width: thick;</span></p><p class="example">テキストに<span class="under-line thick">アンダーライン</span>を引きます。</p>
<p>・pxで指定<span class="code">border-bottom-width: 2px;</span></p><p class="example">テキストに<span class="under-line width-px">アンダーライン</span>を引きます。</p>
<p>・emで指定<span class="code">text-decoration-thickness: .2em;</span></p><p class="example">テキストに<span class="under-line width-em">アンダーライン</span>を引きます。</p>

<h2>位置の調整</h2>
<p>・指定なし</p><p class="example">テキストに<span class="under-line">アンダーライン</span>を引きます。</p>
<p>・paddingで下側に移動<span class="code">padding-bottom: 10px;</span></p><p class="example">テキストに<span class="under-line down">アンダーライン</span>を引きます。</p>
<p>・line-heightの調整で上側に移動<span class="code">display: inline-block; line-height: .3;</span></p><p class="example">テキストに<span class="under-line line-height">アンダーライン</span>を引きます。</p>
<p>・擬似要素で上側に移動</p><p class="example">テキストに<span class="up">アンダーライン</span>を引きます。</p>


<h2>スタイルの変更(border-bottom-style)</h2>
<p>・指定なし<span class="code">(border-bottom-style: none;)</span></p><p class="example">テキストに<span class="under-line none">アンダーライン</span>を引きます。</p>
<p>・solid<span class="code">border-bottom-style: solid;</span></p><p class="example">テキストに<span class="under-line solid">アンダーライン</span>を引きます。</p>
<p>・double<span class="code">border-bottom-style: double;</span></p><p class="example">テキストに<span class="under-line double">アンダーライン</span>を引きます。</p>
<p>・dotted<span class="code">border-bottom-style: dotted;</span></p><p class="example">テキストに<span class="under-line dotted">アンダーライン</span>を引きます。</p>
<p>・dashed<span class="code">border-bottom-style: dashed;</span></p><p class="example">テキストに<span class="under-line dashed">アンダーライン</span>を引きます。</p>
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CSS 

              
                body {
  padding: 20px;
}

h2 {
  margin-top: 70px;
}

.code {
  margin-left: 5px;
  padding: 3px 6px;
  background: #ddd;
  color: #EC1B4B;
}

.example {
  margin-left: 40px;
}

.under-line {
  border-bottom: solid;
}

.color-name {
  border-bottom-color: red;
}

.hex {
  border-bottom-color: #FF7403;
}

.rgba {
  border-bottom-color: rgba(172, 54, 173, .5);
}

.thin {
  border-bottom-width: thin;
}

.thick {
  border-bottom-width: thick;
}

.width-px {
  border-bottom-width: 2px;
}

.width-em {
  border-bottom-width: .4em;
}

.down {
  padding-bottom: 10px;
}

.line-height {
  display: inline-block;
  line-height: .3;
}

.up {
  position: relative;
}

.up:after {
  content: '';
  width: 7em;
  position: absolute;
  bottom: 5px;
  left: 0;
  border-bottom: solid;
}

.none {
  border-bottom-style: none;
}

.solid {
  border-bottom-style: solid;
}

.double {
  border-bottom-style: double;
}

.dotted {
  border-bottom-style: dotted;
}

.dashed {
  border-bottom-style: dashed;
}
!

JS
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999px

Console