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HTML

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Insecure Resource

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CSS

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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

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Vendor Prefixing

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JavaScript

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Babel includes JSX processing.

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HTML 

              
                 <div class="wrapper">
    <section>
      <h1>絶対位置の取得</h1>
      <p>任意の要素の絶対位置を取得するデモ。<br>
      
        絶対位置は右上の赤字部分に表示。
      </p>
      <p>
        位置を取得した要素はページの下部。<br>
        スクロールして確認してください。<br>
      </p>
    </section>

    <section>
      <h2>下にスクロールしてください</h2>
      <p>Scroll down to the bottom.</p>
      <p>下にスクロールしてください。<br>
        Scroll down to the bottom.<br>
        下にスクロールしてください。<br>
        Scroll down to the bottom.<br>
        下にスクロールしてください。<br>
        Scroll down to the bottom.<br>
        下にスクロールしてください。<br>
        Scroll down to the bottom.<br>
        下にスクロールしてください。<br>
        Scroll down to the bottom.<br>
      </p>
    </section>

    <section>
      <h2>下にスクロールしてください</h2>
      <p>Scroll down to the bottom.</p>
      <p>下にスクロールしてください。<br>
        Scroll down to the bottom.<br>
        下にスクロールしてください。<br>
        Scroll down to the bottom.<br>
        下にスクロールしてください。<br>
        Scroll down to the bottom.<br>
        下にスクロールしてください。<br>
        Scroll down to the bottom.<br>
        下にスクロールしてください。<br>
        Scroll down to the bottom.<br>
      </p>
    </section>

    <div class="target">
      ターゲット<br>
      <span>
      赤い上線の位置が絶対位置です。<br>
      現在の位置と等しくなります。<span>
    </div>

    <section>
      <h2>上にスクロールしてください</h2>
      <p>Scroll up</p>
      <p>
        Scroll up<br>
        上にスクロールしてください。<br>
        Scroll up<br>
        上にスクロールしてください。<br>
        Scroll up<br>
        上にスクロールしてください。<br>
        Scroll up<br>
        上にスクロールしてください。<br>
        Scroll up<br>
        上にスクロールしてください。<br>
        Scroll up<br>
        上にスクロールしてください。<br>
        Scroll up<br>
        上にスクロールしてください。<br>
        Scroll up<br>
        上にスクロールしてください。<br>
      </p>
    </section>
    <section>
      <h2>上にスクロールしてください</h2>
      <p>Scroll up</p>
      <p>
        Scroll up<br>
        上にスクロールしてください。<br>
        Scroll up<br>
        上にスクロールしてください。<br>
        Scroll up<br>
        上にスクロールしてください。<br>
        Scroll up<br>
        上にスクロールしてください。<br>
        Scroll up<br>
        上にスクロールしてください。<br>
        Scroll up<br>
        上にスクロールしてください。<br>
        Scroll up<br>
        上にスクロールしてください。<br>
        Scroll up<br>
        上にスクロールしてください。<br>
      </p>
    </section>
    <section>
      <h2>上にスクロールしてください</h2>
      <p>Scroll up</p>
      <p>
        Scroll up<br>
        上にスクロールしてください。<br>
        Scroll up<br>
        上にスクロールしてください。<br>
        Scroll up<br>
        上にスクロールしてください。<br>
        Scroll up<br>
        上にスクロールしてください。<br>
        Scroll up<br>
        上にスクロールしてください。<br>
        Scroll up<br>
        上にスクロールしてください。<br>
        Scroll up<br>
        上にスクロールしてください。<br>
        Scroll up<br>
        上にスクロールしてください。<br>
      </p>
    </section>

  </div>

  <div class="position">
    <div class="position-abs">
      絶対位置:<span></span>
    </div>
    <div class="position-scrolled">
      現在の位置:<span> 0px</span>
    </div>
    <div class="position-desc">
       ※上の青線が<br>現在の位置
    </div>
  </div>

  <div class="currentPosition"></div>
!

CSS 

              
                @charset "utf-8";

:root {
  font-size: 1vw;
}

body {
  background-color: #ffffeb;
}

.wrapper {
  width: 82%;
  margin: auto;
}

section {
  &:not(:last-child) {
    margin-bottom: 8rem;
  }
}

h1 {
  font-size: 3.4rem;
  padding-left: 0.5em;
  border-left: 1.2rem solid red;
  margin-top: 5rem;
  
  + p {
    font-size: 1.7rem;
    font-weight: bold;
  }
  
}

h2 {
  font-size: 2rem;
  margin-bottom: 1.3rem;
  
  padding-left: 0.5rem;
  border-left: 0.6rem solid red;
  + p {
    font-size: 1.4rem;
    font-weight: bold;
  }
}

p {
  font-size: 1.4rem;
  line-height: 1.8;
  max-width: 60%;
}

.target {
  width: 28%;
  margin-top: 3rem;
  background-color: orange;
  font-size: 2.4rem;
  text-align: center;
  font-weight: bold;
  padding: 5vw;
  border-top: 2rem solid red;
  margin-bottom: 5rem;
  
  > span {
    font-weight: normal;
    font-size: 1.4rem;
  }
}

.position {
  text-align: right;
  position: fixed;
  top: 3rem;
  right: 10%;
  padding: 1rem;
  font-size: 2.5rem;
  
  span {
    font-weight: bold;
  }

  &-abs {
    color: red;
  }
  
  &-desc {
    font-size: 1.6rem;
  }

}

.currentPosition {
  position: fixed;
  width: 100%;
  height: 2rem;
  background-color: blue;
  opacity: .6;
  top: 0;
  left: 0;
}
!

JS 

              
                window.addEventListener('DOMContentLoaded', () => {
  //target
  const target = document.querySelector<HTMLDivElement>('.target')
  
  //main process
  const height = target!.getBoundingClientRect().top + window.scrollY
  
  //for display
  document.querySelector<HTMLSpanElement>('.position-abs > span')!.textContent = Math.round(height) + "px"
  const scrolled = document.querySelector<HTMLSpanElement>('.position-scrolled > span')

  //current position
  window.addEventListener('scroll', () => {
    scrolled!.textContent = String(Math.round(window.scrollY)) + "px"
  })
})
!
999px

Console