下拉列表移动其他元素

Question

这里我有一个完全使用 vanilla JavaScript 制作的下拉菜单。 但是当我点击下拉按钮时，它会移动其他元素。

let dropdownBtn = document.querySelector("button.dropdown-btn");
let itemListWrapper = document.querySelector("div.item-list-wrapper");

dropdownBtn.addEventListener("click", () => {
  if (itemListWrapper.style.display === "none") {
    itemListWrapper.style.display = "block";
  } else {
    if (itemListWrapper.style.display === "block" || itemListWrapper.style.display === "") {
      itemListWrapper.style.display = "none";
    }
  }
});

function continuouslyClickDropdownBtn() {
  dropdownBtn.click();
  setTimeout(() => {
    continuouslyClickDropdownBtn();
  }, 750);
}

continuouslyClickDropdownBtn();

.container {
  background-color: lightblue;
  height: 200px;
  padding: 0 2em;
}

.dropdown-wrapper {
  width: fit-content;
  background-color: hsla(0, 0%, 95%, 0.9);
  padding: 0.3em;
  border-radius: 0.3em;
  position: relative;
}

.dropdown-btn {
  border-radius: 0.3em;
  width: 100%;
  height: 1.75em;
  font-size: 1.25em;
  cursor: pointer;
}

.item-list-wrapper {
  margin-top: 0.5em;
}

.dropdown-item-list {
  list-style: none;
  padding: 0;
  margin: 0;
  display: flex;
  flex-direction: column;
  gap: 0.1em
}

.dropdown-item {
  font-size: 1em;
  width: 100%;
  padding: 0.2em 0;
  display: flex;
  flex-direction: row;
  cursor: pointer;
}

.dropdown-item:hover {
  background-color: hsla(0, 0%, 80%, 1);
  font-weight: bold;
}

.dropdown-item span {
  flex-grow: 1;
  padding: 0 1empx;
}

<div class="container">
  <p>upper text</p>
  <div class="dropdown-wrapper">
    <button class="dropdown-btn">Media Quality</button>
    <div class="item-list-wrapper">
      <ul class="dropdown-item-list">
        <li class="dropdown-item">
          <span>360p</span>
        </li>
        <li class="dropdown-item">
          <span>720p</span>
        </li>
        <li class="dropdown-item">
          <span>1080p</span>
        </li>
      </ul>
    </div>
  </div>
  <p>bottom text</p>
</div>

我尝试添加这个 CSS：

.item-list-wrapper {
  margin-top: 0.5em;
  position: absolute;
}

然后它会从所有项目中删除背景颜色。 即使将 background-color: hsla(0, 0%, 95%, 0.9); 添加到类中，它也只会将其添加到项目的宽度中。 一旦打开，我无法让背景颜色环绕整个下拉菜单。

如何解决这个问题？

Answer 1

对.item-list-wrapper 使用绝对定位，添加额外的规则来规范这个下拉菜单的显示。将此选择器与 css 规则一起使用：

.item-list-wrapper {
    position: absolute;
    left: 0;
    right: 0;
    background-color: inherit;
    padding: inherit;
    border-radius: 0 0 0.3em 0.3em;
}

通过这些规则，您可以继承背景颜色，使宽度相对于父级，并为下拉菜单的底部设置边框半径。

let dropdownBtn = document.querySelector("button.dropdown-btn");
let itemListWrapper = document.querySelector("div.item-list-wrapper");

dropdownBtn.addEventListener("click", () => {
    if (itemListWrapper.style.display === "none") {
        itemListWrapper.style.display = "block";
    } else {
        if (itemListWrapper.style.display === "block" || itemListWrapper.style.display === "") {
            itemListWrapper.style.display = "none";
        }
    }
});

function continuouslyClickDropdownBtn() {
    dropdownBtn.click();
    setTimeout(() => {
        continuouslyClickDropdownBtn();
    }, 750);
}

continuouslyClickDropdownBtn();

.container {
    background-color: lightblue;
    height: 200px;
    padding: 0 2em;
}

.dropdown-wrapper {
    width: fit-content;
    background-color: hsla(0, 0%, 95%, 0.9);
    padding: 0.3em;
    border-radius: 0.3em;
    position: relative;
}

.dropdown-btn {
    border-radius: 0.3em;
    width: 100%;
    height: 1.75em;
    font-size: 1.25em;
    cursor: pointer;
}

.item-list-wrapper {
    position: absolute;
    left: 0;
    right: 0;
    background-color: inherit;
    padding: inherit;
    border-radius: 0 0 0.3em 0.3em;
}

.dropdown-item-list {
    list-style: none;
    padding: 0;
    margin: 0;
    display: flex;
    flex-direction: column;
    gap: 0.1em;
}

.dropdown-item {
    font-size: 1em;
    width: 100%;
    padding: 0.2em 0;
    display: flex;
    flex-direction: row;
    cursor: pointer;
}

.dropdown-item:hover {
    background-color: hsla(0, 0%, 80%, 1);
    font-weight: bold;
}

.dropdown-item span {
    flex-grow: 1;
    padding: 0 1empx;
}

<div class="container">
    <p>upper text</p>
    <div class="dropdown-wrapper">
        <button class="dropdown-btn">Media Quality</button>
        <div class="item-list-wrapper">
            <ul class="dropdown-item-list">
                <li class="dropdown-item">
                    <span>360p</span>
                </li>
                <li class="dropdown-item">
                    <span>720p</span>
                </li>
                <li class="dropdown-item">
                    <span>1080p</span>
                </li>
            </ul>
        </div>
    </div>
    <p>bottom text</p>
</div>

Answer 2

一种方法是拥有一个inner-wrapper 并将其设置为position:fixed 您必须设置 dropdown-wrapper 的高度，以便该元素在页面上仍然存在块

let dropdownBtn = document.querySelector("button.dropdown-btn");
let itemListWrapper = document.querySelector("div.item-list-wrapper");

dropdownBtn.addEventListener("click", () => {
  if (itemListWrapper.style.display === "none") {
    itemListWrapper.style.display = "block";
  } else {
    if (itemListWrapper.style.display === "block" || itemListWrapper.style.display === "") {
      itemListWrapper.style.display = "none";
    }
  }
});

function continuouslyClickDropdownBtn() {
  dropdownBtn.click();
  setTimeout(() => {
    continuouslyClickDropdownBtn();
  }, 750);
}

continuouslyClickDropdownBtn();

.container {
  background-color: lightblue;
  height: 200px;
  padding: 0 2em;
}

.dropdown-wrapper {
  position: relative;
  height: 40px;
}

.inner-wrapper {
  position: fixed;
  width: fit-content;
  background-color: hsla(0, 0%, 95%, 0.9);
  padding: 0.3em;
  border-radius: 0.3em;
}

.dropdown-btn {
  border-radius: 0.3em;
  width: 100%;
  height: 1.75em;
  font-size: 1.25em;
  cursor: pointer;
}

.item-list-wrapper {
  margin-top: 0.5em;
}

.dropdown-item-list {
  list-style: none;
  padding: 0;
  margin: 0;
  display: flex;
  flex-direction: column;
  gap: 0.1em
}

.dropdown-item {
  font-size: 1em;
  width: 100%;
  padding: 0.2em 0;
  display: flex;
  flex-direction: row;
  cursor: pointer;
}

.dropdown-item:hover {
  background-color: hsla(0, 0%, 80%, 1);
  font-weight: bold;
}

.dropdown-item span {
  flex-grow: 1;
  padding: 0 1empx;
}

<div class="container">
  <p>upper text</p>
  <div class="dropdown-wrapper">
    <div class="inner-wrapper">
      <button class="dropdown-btn">Media Quality</button>
      <div class="item-list-wrapper">
        <ul class="dropdown-item-list">
          <li class="dropdown-item">
            <span>360p</span>
          </li>
          <li class="dropdown-item">
            <span>720p</span>
          </li>
          <li class="dropdown-item">
            <span>1080p</span>
          </li>
        </ul>
      </div>
    </div>
  </div>
  <p>bottom text</p>
</div>