jQuery Mastery: Plugins, Performance & Migrating to Modern JS
Audit, speed up and modernise a fictional storefront's legacy jQuery: selector cost, caching, delegation, namespaces, plugin authoring, Deferreds, effects, throttling and a measured move to vanilla JavaScript, with every answer checked as you go.
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About this course
This advanced course works through the legacy jQuery code of a fictional outdoor storefront. In 22 hands-on labs you read real code and compute what it does: how many elements a selector examines, how many DOM lookups caching saves, which handlers survive a namespaced .off(), what a promise chain logs after a thrown error, and how many requests a debounced search sends. You write chainable $.fn plugins with defaults and one instance per element, then plan the move to modern JavaScript: querySelectorAll, classList, fetch with correct error handling, jQuery Migrate findings and a measured payload budget. A weighted scorecard and a final exam close the course, and the first lesson is free.
Lessons
- Audit a Legacy jQuery Codebase Before You Touch ItFree
- The jQuery Object: Collections, Getters, Setters and Truthiness Locked
- Selector Performance: Right-to-Left Matching and jQuery-Only Extensions Locked
- Cache Your Selections: Counting DOM Lookups in Loops Locked
- Batch DOM Writes: Layout Thrashing and a Single .append() Locked
- Event Delegation: One Handler for Rows That Don't Exist Yet Locked
- Event Namespaces: Unbinding Exactly What You Own Locked
- Bubbling, return false and stopImmediatePropagation Locked
- $.extend: Defaults, Options and the Shallow-Copy Trap Locked
- $.fn Plugins: the IIFE, this.each() and Returning this Locked
- .data() vs data-* Attributes: Caching and Type Conversion Locked
- Stateful Plugins: One Instance per Element, Methods and destroy Locked
- Deferreds I: $.when, Parallel Requests and the Critical Path Locked
- Deferreds II: then vs done, Thrown Errors and Recovery Locked
- Ajax Resilience: Timeouts, Retries and Exponential Backoff Locked
- The Effects Queue: Timelines, .delay() and .stop() Locked
- Throttle and Debounce Scroll, Resize and Input Handlers Locked
- jQuery to Vanilla I: Selecting, Classes, Attributes and Traversal Locked
- jQuery to Vanilla II: $.ajax vs fetch Error Semantics Locked
- Reading Legacy Code: Deprecated APIs and jQuery Migrate Locked
- Measuring the Win: Payload, Download Time and Monthly Transfer Locked
- Capstone: The Migration Scorecard Locked