JarCasting
Lower level API that is used by the ponyfill scroll-into-view-if-needed to compute where (if needed) elements should scroll based on options defined in the spec and the scrollMode: "if-needed" draft spec proposal. Use this if you want the smallest possible bundlesize and is ok with implementing the actual scrolling yourself.
Scrolling SVG elements are supported, as well as Shadow DOM elements. The VisualViewport API is also supported, ensuring scrolling works properly on modern devices. Quirksmode is also supported as long as you polyfill document.scrollingElement.
Install
yarn add compute-scroll-into-view
The UMD build is also available on unpkg:
<script src="https://unpkg.com/compute-scroll-into-view/umd/compute-scroll-into-view.min.js"></script>
You can find the library on window.computeScrollIntoView.
Usage
// es6 import
import computeScrollIntoView from 'compute-scroll-into-view'
// or es5
const computeScrollIntoView = require('compute-scroll-into-view')
const node = document.getElementById('hero')
// same behavior as Element.scrollIntoView({block: "nearest", inline: "nearest"})
// see: https://developer.mozilla.org/en-US/docs/Web/API/Element/scrollIntoView
const actions = computeScrollIntoView(node, {
scrollMode: 'if-needed',
block: 'nearest',
inline: 'nearest',
})
// same behavior as Element.scrollIntoViewIfNeeded(true)
// see: https://developer.mozilla.org/en-US/docs/Web/API/Element/scrollIntoViewIfNeeded
const actions = computeScrollIntoView(node, {
scrollMode: 'if-needed',
block: 'center',
inline: 'center',
})
// Then perform the scrolling, use scroll-into-view-if-needed if you don't want to implement this part
actions.forEach(({ el, top, left }) => {
el.scrollTop = top
el.scrollLeft = left
})
API
computeScrollIntoView(target, options)
options
Type: Object
block
Type: 'start' | 'center' | 'end' | 'nearest'
Default: 'center'
Control the logical scroll position on the y-axis. The spec states that the block direction is related to the writing-mode, but this is not implemented yet in this library. This means that block: 'start' aligns to the top edge and block: 'end' to the bottom.
inline
Type: 'start' | 'center' | 'end' | 'nearest'
Default: 'nearest'
Like block this is affected by the writing-mode. In left-to-right pages inline: 'start' will align to the left edge. In right-to-left it should be flipped. This will be supported in a future release.
scrollMode
Type: 'always' | 'if-needed'
Default: 'always'
This is a proposed addition to the spec that you can track here: https://github.com/w3c/csswg-drafts/pull/1805
This library will be updated to reflect any changes to the spec and will provide a migration path. To be backwards compatible with Element.scrollIntoViewIfNeeded if something is not 100% visible it will count as "needs scrolling". If you need a different visibility ratio your best option would be to implement an Intersection Observer.
boundary
Type: Element | Function
By default there is no boundary. All the parent elements of your target is checked until it reaches the viewport (document.scrollingElement) when calculating layout and what to scroll. By passing a boundary you can short-circuit this loop depending on your needs:
- Prevent the browser window from scrolling.
- Scroll elements into view in a list, without scrolling container elements.
You can also pass a function to do more dynamic checks to override the scroll scoping:
const actions = computeScrollIntoView(target, {
boundary: parent => {
// By default `overflow: hidden` elements are allowed, only `overflow: visible | clip` is skipped as
// this is required by the CSSOM spec
if (getComputedStyle(parent)['overflow'] === 'hidden') {
return false
}
return true
},
})
skipOverflowHiddenElements
Type: Boolean
Default: false
By default the spec states that overflow: hidden elements should be scrollable because it has been used to allow programatic scrolling. This behavior can sometimes lead to scrolling issues when you have a node that is a child of an overflow: hidden node.
This package follows the convention adopted by Firefox of setting a boolean option to not scroll all nodes with overflow: hidden set.
TypeScript support
This library ships with library definitions for TypeScript.