How can I observe how the current section is viewed by a user on a web page?

Question

When a user views a web page, they scroll through different sections of the page by scrolling. In the Bootstrap documentation , the bs-docs-sidenavList Item changes color to reflect which section is currently “active” (displayed on the screen).

• Does this type of observation have a name (or names)?
• Does the DOM have any properties that track the location of an element?
• If not, are there any common plugins / small libraries to take advantage of this information?

Answer 1

, Bootstrap Scrollspy. getBoundingClientRect function .