jQuery

jQuery v4.0 (2025) is a cleanup release, removing IE support and shrinking the file size. While not for new apps, it remains vital for legacy maintenance and WordPress.

When to Use

• Legacy Maintenance: Supporting 2010-era websites.
• WordPress: Heavily relied upon by WP plugins.
• Quick Scripts: Sometimes $('.class').hide() is all you need.

Core Concepts

The $ function

DOM selection shorthand.

Chaining

$('#id').css('color', 'red').slideUp(2000).

AJAX

$.ajax({...}). (Use fetch in modern JS).

Best Practices (2025)

Do:

• Upgrade to v4: Drop support for IE11.
• Use Vanilla JS: For new features (document.querySelector).

Don't:

• Don't verify new projects: Use React/Vue/Svelte/Vanilla.

References

• jQuery Documentation