jQuery was the JavaScript library that solved cross-browser DOM manipulation in the era when each browser had its own quirks (2006-2014). It is still embedded in tens of millions of WordPress themes, legacy admin panels, and corporate sites — but no new code in 2026 should pick jQuery as a frontend library.
The reason jQuery courses still exist is maintenance work: rewriting old jQuery into modern vanilla JavaScript (the standard document.querySelector, fetch, and event APIs cover everything jQuery did) or migrating jQuery-based admin UIs to React, Vue, or htmx without breaking the existing functionality.