JavaScript · DOM APIs

IntersectionObserver

Reports when elements enter or leave the viewport. Ideal for lazy loading.

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Syntax

new IntersectionObserver(callback)

Example

Try it

const observer = new window.IntersectionObserver(() => {});
observer.observe(document.createElement("div"));
console.log("observing");

Reference pages are the quick answer. The course explains the why, shows the full example and ends with a challenge.