Infinite scrolling is unusual. Most implementations are “almost infinite” to avoid excessive DOM length (memory).

• Infinite scrolling: Limits content to an arbitrarily large amount to avoid exhausting memory.

• Virtual scrolling: Unload everything except the visible viewport + a top and bottom offset. Pad the rest.

Virtual scrolling is infinite, but breaks auxiliary actions ( CTRL + F ) because what’s on the screen is the content.

document.addEventListener("scroll", function() {
  console.log(document.querySelectorAll('*').length)
});

The most popular library appears to be https://infinite-scroll.com.