JavaScript: The Hard Parts, v2 vs Complete Intro to React v9

Goes deep on the JavaScript runtime model — thread of execution, the call stack, closure, the event loop, Promises and prototypes/classes — across roughly 6.5 hours. Reviewers consistently say it explains how JavaScript works "under the hood" rather than just syntax.

Will Sentance (Codesmith founder) is the most-praised element. Learners cite his blackboard diagrams, the "backpack" analogy for closure, and a Socratic, audience-paced delivery. The same intense, repetitive style is the one thing a minority find tiring.

Requires a $39/month Frontend Masters subscription rather than a one-time purchase — strong value if you use the wider catalog, weaker if you only want this one course. The course is included in the standard subscription.

This is a conceptual, exercise-and-whiteboard course, not a project build. There is no portfolio-worthy capstone, which some learners miss. The exercises are effective for drilling mental models but produce no artefact.

The mental models — call stack, closure, the event loop, async behaviour — directly explain bugs developers hit daily. Experienced developers report the course clarified concepts they had used for years without fully understanding.

v9 covers React 18 and 19 features (form actions, Suspense, the React Compiler) plus a modern Vite + TanStack Router + TanStack Query stack. Praised for currency, with a minority of long-term Frontend Masters subscribers flagging that other courses in the catalog can drift.

Brian Holt is the most consistently praised aspect across nine years of Hacker News mentions. Learners use words like 'excellent', 'great', and 'brilliant'. His pet adoption project framing is repeatedly cited as memorable.

Requires a Frontend Masters subscription (currently $39/month), which is consistently described as worth it if you complete more than one course per month. Less competitive against free alternatives if you only want a single React intro.

The single build-along project (an e-commerce app in v9, evolved from the pet adoption app of earlier versions) is praised for being non-trivial and integrating real ecosystem tools (TanStack Query, Vitest) rather than toy examples.

Holt spends real time on tooling (Vite, ESLint, Prettier, code-splitting, Vitest) and modern ecosystem choices, which is the single most-cited reason people say his courses transferred well to their day jobs.