CSS オーバーフロー

<article>
  <fieldset>
    <legend>オプションを選択してください:</legend>
    <label
      ><code>overflow</code>:
      <select id="overflowValue">
        <option>hidden</option>
        <option>clip</option>
        <option>scroll</option>
        <option>auto</option>
        <option selected>visible</option>
        <option>overlay</option>
      </select>
    </label>
    <label>
      <code>overflow-clip-margin</code>:
      <input type="number" id="ocm" value="1" min="0" max="10" />
      <code>em</code>
    </label>
    <label
      ><input type="checkbox" id="wide" /> <code>width</code>:
      <code>20em</code> または <code>40em</code></label
    >
    <fieldset>
      <legend>プログラムによるスクロール:</legend>
      <label
        >ScrollLeft:
        <input type="range" min="0" max="100" value="0" id="scrollL"
      /></label>
      <label
        >ScrollTop:
        <input type="range" min="0" max="100" value="0" id="scrollT"
      /></label>
    </fieldset>
  </fieldset>
  <pre class="visible">&nbsp;
    Oh, Rubber Duckie, you're the one
    You make bath time lots of fun
    Rubber Duckie, I'm awfully fond of you

    Rubber Duckie, joy of joys
    When I squeeze you, you make noise
    Rubber Duckie, you're my very best friend, it's true

    Oh, every day when I make my way to the tubby
    I find a little fella who's cute and yellow and chubby
    Rub-a-dub-dubby

    <a href="#">Rubber Duckie</a>, you're so fine
    And I'm lucky that you're mine
    Rubber Duckie, I'm awfully fond of you
      </pre>
</article>

article {
  display: flex;
  gap: 1em;
}

label {
  display: block;
  white-space: nowrap;
}

pre {
  border: 2px dashed crimson;
  height: 150px;
  width: 20em;
  margin-bottom: 3em;
  overflow-clip-margin: 1em;
  text-align: center;
}

.wide {
  width: 40em;
}

::before {
  font-weight: bold;
  color: white;
  background: crimson;
  display: inline-block;
  min-width: 50%;
  padding: 3px 5px;
  box-sizing: border-box;
}

.hidden {
  overflow: hidden;
}
.hidden::before {
  content: "hidden: ";
}

.clip {
  overflow: clip;
}
.clip::before {
  content: "clip: ";
}

.scroll {
  overflow: scroll;
}
.scroll::before {
  content: "scroll: ";
}

.auto {
  overflow: auto;
}
.auto::before {
  content: "auto: ";
}

.overlay {
  overflow: clip;
  overflow: overlay;
}
.overlay::before {
  content: "overlay (or clip if not supported): ";
}

.visible {
  overflow: visible;
}
.visible::before {
  content: "visible: ";
}

article:not(:has(pre.clip)) > fieldset > label:nth-of-type(2),
article:not(:has(pre.hidden, pre.scroll, pre.auto, pre.overlay))
  fieldset
  fieldset {
  opacity: 20%;
  pointer-events: none;
}

const pre = document.querySelector("pre");
const val = document.getElementById("overflowValue");
const check = document.getElementById("wide");
const ocm = document.getElementById("ocm");
const scrollL = document.getElementById("scrollL");
const scrollT = document.getElementById("scrollT");

val.addEventListener("change", () => {
  if (pre.classList.contains("wide")) {
    pre.className = `wide ${val.value}`;
  } else {
    pre.className = `${val.value}`;
  }
  scrollExample();
  clipMargin();
});

wide.addEventListener("change", () => {
  pre.classList.toggle("wide");
  scrollExample();
});

ocm.addEventListener("change", () => {
  clipMargin();
});

scrollL.addEventListener("change", () => {
  scrollExample();
});
scrollT.addEventListener("change", () => {
  scrollExample();
});

function scrollExample() {
  pre.scrollTo({
    top: scrollT.value,
    left: scrollL.value * 2,
    behavior: "smooth",
  });
}

function clipMargin() {
  pre.style.overflowClipMargin = `${ocm.value}em`;
}