In browsers that support the Intersection Observer, this library lets you find out when an element of yours is in viewport. The viewport itself is configurable. It can be the window or any other element in the DOM. Only requirement is that the element who visibility you want to check must be a child of the element you choose as your viewport.
npm install observe-element-in-viewport
or grab it directly from unpkg
and include it in your html as
<!-- will fetch UMD build --> <script src="https://unpkg.com/observe-element-in-viewport"></script> <!-- or below to fetch the es module build --> <script type="module" src="https://unpkg.com/observe-element-in-viewport?module"></script>
or directly in your javascript as below which will import the latest version of observe-element-in-viewport
.
import { observeElementInViewport, isInViewport } from 'https://unpkg.com/observe-element-in-viewport?module'
Observing aFor more information on how to get specific versions from
unpkg
, have a look at their webpage.
target
element
import { observeElementInViewport } from 'observe-element-in-viewport' // to use window as viewport, pass this option as null const viewport = document.querySelector('.viewport') // element whose visibility we want to track const target = document.querySelector('.target') // handler for when target is in viewport const inHandler = (entry, unobserve, targetEl) => console.log('In viewport') // handler for when target is NOT in viewport const outHandler = (entry, unobserve, targetEl) => console.log('Not in viewport') // the returned function, when called, stops tracking the target element in the // given viewport const unobserve = observeElementInViewport(target, inHandler, outHandler, { // set viewport viewport, // decrease viewport top by 100px // similar to this, modRight, modBottom and modLeft exist modTop: '-100px' // threshold tells us when to trigger the handlers. // a threshold of 90 means, trigger the inHandler when atleast 90% // of target is visible. It triggers the outHandler when the amount of // visible portion of the target falls below 90%. // If this array has more than one value, the lowest threshold is what // marks the target as having left the viewport threshold: [90] })One time query to check if
target
element is in viewport
import { isInViewport } from 'observe-element-in-viewport' // element whose visibility we want to track const target = document.querySelector('.target') // Using window as viewport, it will check the target element's // visibility and log true or false. // This function accepts a second parameter which is the same // as the first parameter to observeElementInViewport fn i.e., // the options object. console.log(await isInViewport(target))
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