Intermediate React, v6: React Server Components, Hooks & Performance vs JavaScript: The Hard Parts, v2

v6 is rebuilt around React 19 — render modes, React Server Components both from scratch and inside Next.js, transitions, optimistic and deferred values. Reviewers praise the "under the hood" RSC explanation. The honest caveat is that hooks, TypeScript and Redux content from older versions has been narrowed in favour of the RSC and performance focus.

Brian Holt is the single most consistently praised element across nine years of Hacker News mentions and official testimonials. Learners with one to three years of React experience still call the teaching "fun", "interactive" and clear. Official course rating sits at 4.7 stars.

Requires a Frontend Masters subscription ($39/month or $390/year). At a 6h22m runtime this single course is only worth the price if you pair it with the wider catalog or complete it inside one billing month. Less competitive against the free React docs if you want one course alone.

Unlike the project-based Complete Intro, the Intermediate course is modular — unrelated concepts taught as standalone lessons (RSCs from scratch, RSCs with Next.js, performance demos). Reviewers find the build-from-scratch RSC segment genuinely illuminating, but there is no single cohesive app to carry away as a portfolio artefact.

The RSC and performance material maps directly onto what teams are shipping with Next.js App Router in 2026. Learners specifically credit it with demystifying what Next.js is doing under the hood — transferable knowledge rather than tutorial-only skills.

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.