jQuery 4.0.0 Turns 20: The Library That Revolutionized JavaScript

Hello HaWkers, one of the most influential libraries in web development history has just reached an impressive milestone: jQuery turns 20 and celebrates with the release of version 4.0.0. Even in an era dominated by modern frameworks like React, Vue, and Svelte, jQuery remains present on millions of websites worldwide.

Have you ever stopped to think about the impact a simple library had on how we write JavaScript today? Let's explore this journey and understand why jQuery still matters in 2026.

The History of jQuery

John Resig released jQuery in January 2006, at a time when JavaScript was synonymous with frustration for developers.

The Problem jQuery Solved

Before jQuery:

Each browser implemented JavaScript differently
Internet Explorer, Firefox, and Safari had incompatible APIs
DOM manipulation was verbose and error-prone
AJAX was complex and inconsistent

After jQuery:

A unified API that worked across all browsers
Concise and chainable syntax
AJAX simplified to one line
Accessible animations and effects

Evolution Timeline

2006: jQuery 1.0 - "Write less, do more"
2009: jQuery 1.3 - Sizzle selector engine
2013: jQuery 2.0 - Removes IE 6-8 support
2016: jQuery 3.0 - Promises/A+ compliance
2026: jQuery 4.0 - Complete modernization

What's New in jQuery 4.0.0

Version 4.0.0 brings significant changes that modernize the library for current JavaScript.

Main Changes

1. Removed Deprecated APIs:

jQuery.isArray() removed (use Array.isArray())
jQuery.isFunction() removed (use typeof)
jQuery.isNumeric() removed
jQuery.type() removed

2. Browser Support:

Minimum: Chrome 99+, Firefox 91+, Safari 15+
IE completely removed
Focus on evergreen browsers

3. Reduced Size:

Main bundle: 28KB minified
Slim build: 19KB
15% reduction compared to 3.x

Modern Code Examples

// jQuery 4.0.0 - Modern DOM manipulation
$('.cards')
  .find('.card')
  .filter(':visible')
  .addClass('highlighted')
  .on('click', async function() {
    const data = await $.get('/api/card/' + $(this).data('id'));
    $(this).html(data.content);
  });

// Optimized event delegation
$('#app').on('click', '[data-action]', function(e) {
  const action = $(this).data('action');
  const target = $(this).data('target');

  switch(action) {
    case 'toggle':
      $(target).slideToggle(300);
      break;
    case 'remove':
      $(this).closest('.item').fadeOut(200, function() {
        $(this).remove();
      });
      break;
  }
});

// Simplified AJAX with jQuery 4.0
async function fetchUserData(userId) {
  try {
    const user = await $.ajax({
      url: `/api/users/${userId}`,
      method: 'GET',
      dataType: 'json'
    });

    // Update UI with data
    $('#user-name').text(user.name);
    $('#user-email').text(user.email);
    $('#user-avatar').attr('src', user.avatarUrl);

    return user;
  } catch (error) {
    console.error('Error fetching user:', error);
    $('#error-message').text('Failed to load data').show();
  }
}

// POST with FormData
$('#contact-form').on('submit', async function(e) {
  e.preventDefault();

  const formData = new FormData(this);

  const response = await $.ajax({
    url: '/api/contact',
    method: 'POST',
    data: formData,
    processData: false,
    contentType: false
  });

  if (response.success) {
    $(this).html('<p class="success">Message sent!</p>');
  }
});

jQuery vs Vanilla JavaScript in 2026

A frequent question: does it still make sense to use jQuery when modern JavaScript offers powerful native APIs?

Syntax Comparison

Element selector:

// jQuery
$('.card').first();

// Vanilla JS
document.querySelector('.card');

Multiple elements:

// jQuery
$('.cards').each(function() {
  $(this).addClass('active');
});

// Vanilla JS
document.querySelectorAll('.cards').forEach(el => {
  el.classList.add('active');
});

Event listeners:

// jQuery - simple delegation
$('#list').on('click', '.item', handler);

// Vanilla JS - more verbose
document.getElementById('list').addEventListener('click', function(e) {
  if (e.target.matches('.item')) {
    handler.call(e.target, e);
  }
});

When jQuery Still Makes Sense

1. Legacy Projects:

Millions of WordPress sites use jQuery
Complete migration can be expensive
Maintaining compatibility is pragmatic

2. Rapid Prototyping:

Concise syntax speeds up development
Less boilerplate than vanilla JS
Ready-to-use plugins

3. Mixed Teams:

Developers already know jQuery
Minimal learning curve
Extensive documentation

4. Projects Without Build System:

Works with a single script tag
No need for bundlers
Simplified deployment

jQuery's Legacy

jQuery's impact goes far beyond the library itself.

Influence on Modern JavaScript

Many native APIs were inspired by jQuery:

QuerySelector:

// jQuery inspired
document.querySelector('.class');
document.querySelectorAll('.class');

// Before it required
document.getElementsByClassName('class');
document.getElementById('id');

ClassList API:

// Inspired by .addClass(), .removeClass()
element.classList.add('active');
element.classList.remove('active');
element.classList.toggle('active');

Fetch API:

// Inspired by $.ajax()
fetch('/api/data')
  .then(response => response.json())
  .then(data => console.log(data));

2026 Usage Statistics

Metric	Value
Sites using jQuery	77% of sites with JS
npm downloads/week	6.2 million
GitHub repositories	2.1 million
Stack Overflow questions	1.4 million

💡 Context: Even though it's considered "legacy," jQuery is still the most used JavaScript library in the world.

Popular Plugins That Depend on jQuery

Many popular tools still require jQuery:

Bootstrap 4.x - CSS Framework
Select2 - Enhanced selects
DataTables - Interactive tables
Slick - Responsive carousels
Magnific Popup - Lightboxes
jQuery UI - Interface components

Migrating to jQuery 4.0

If you have projects on earlier versions, here's how to migrate.

Migration Tool

// Include jQuery Migrate to identify problems
<script src="https://code.jquery.com/jquery-4.0.0.min.js"></script>
<script src="https://code.jquery.com/jquery-migrate-4.0.0.min.js"></script>

// Migrate displays warnings in the console for removed APIs
// JQMIGRATE: jQuery.isFunction() is deprecated

Migration Checklist

1. Identify deprecated APIs:

// Search your code for:
// $.isArray, $.isFunction, $.isNumeric, $.type
// .andSelf(), .size(), .context
// Callbacks: $.Callbacks without 'unique'

2. Update selectors:

// Before (deprecated)
$(':first')
$(':last')

// After
$().first()
$().last()

3. Test events:

// Remove .load() for images
// Use .on('load') instead
$('img').on('load', function() {
  // handler
});

The Future of jQuery

What to expect in the coming years?

2026-2027 Roadmap

Planned:

Web Components support
Integration with Custom Elements
APIs for Shadow DOM
Updated TypeScript definitions

Under Discussion:

jQuery as native ES Module
Improved tree-shaking
"Micro" version under 10KB

When Not to Use jQuery

Despite its utility, there are scenarios where jQuery is not ideal:

Avoid jQuery for:

Complex SPA applications (use React/Vue/Svelte)
Projects with modern build systems
Teams focused on maximum performance
New green-field projects

Conclusion

jQuery 4.0.0 marks two decades of a library that fundamentally changed how we write JavaScript. Even in 2026, with all modern alternatives available, jQuery remains relevant for its simplicity, vast ecosystem, and presence in millions of legacy projects.

Key points:

jQuery 4.0.0 removes deprecated APIs and focuses on modern browsers
The library inspired many native JavaScript APIs
It's still the most used JS library, with 77% of sites
Makes sense for legacy projects, prototyping, and teams that already know it
For new and complex projects, modern frameworks are more suitable

jQuery taught us that simplicity is powerful. Even if you never write $() in your code again, the lessons it brought to web development live on in the APIs we use daily.

If you want to understand more about the modern JavaScript ecosystem, I recommend reading ESM (ES Modules): Complete Adoption in JavaScript 2026.