Element.scrollTop

Baseline Widely available

This feature is well established and works across many devices and browser versions. It’s been available across browsers since September 2020.

Element.scrollTop 屬性可以設置和獲取元素被向上捲動的高度(pixels). 元素的 scrollTop 是元素頂端和能被看見的最頂端之間的距離. 當元素並未產生滾動條, 那麼 scrollTop 的值預設為 0.

表達式

js
// 獲得已經被滾動的距離(pixels)
var intElemScrollTop = someElement.scrollTop;

intElemScrollTop 為 element已經被滾動的距離(pixels ).

js
// 設置已經被滾動的距離(pixels)
element.scrollTop = intValue;

scrollTop 可以被設置為任何和正整數, 注意事項:

  • 如果元素不能滾動, scrollTop 被設置為 0.
  • 如果設置的值小於 0, scrollTop 被設置為 0.
  • 如果設置的值大於內容可以被滾動的距離, scrollTop 被設置為最大值.

範例

Scrolling an element

In this example, try scrolling the inner container with the dashed border, and see how the value of scrollTop changes.

HTML

html
<div id="container">
  <div id="scroller">
    <p>
      Far out in the uncharted backwaters of the unfashionable end of the
      western spiral arm of the Galaxy lies a small unregarded yellow sun.
      Orbiting this at a distance of roughly ninety-two million miles is an
      utterly insignificant little blue green planet whose ape-descended life
      forms are so amazingly primitive that they still think digital watches are
      a pretty neat idea.
    </p>
  </div>
</div>

<div id="output">scrollTop: 0</div>

CSS

css
#scroller {
  overflow: scroll;
  height: 150px;
  width: 150px;
  border: 5px dashed orange;
}

#output {
  padding: 1rem 0;
}

JavaScript

js
const scroller = document.querySelector("#scroller");
const output = document.querySelector("#output");

scroller.addEventListener("scroll", (event) => {
  output.textContent = `scrollTop: ${scroller.scrollTop}`;
});

結果

規範

Specification
CSSOM View Module
# dom-element-scrolltop

參閱