Runtime Lab

The Runtime Lab makes language and runtime behavior visible instead of abstract.

Initial Focus

• JavaScript event loop
• call stack
• heap
• microtasks and macrotasks
• promises and async flow
• closures and scope

Product Experience

Users should be able to:

• paste or study example code
• step through execution
• inspect stack frames and queued work
• see promise and timer behavior unfold in order
• connect runtime events to rendered output or state changes

Why This Matters

Frontend and full-stack developers often learn syntax faster than runtime behavior. The Runtime Lab is intended to close that gap.

Later Extensions

• Node.js internals
• browser rendering pipeline
• React rendering behavior
• server-client boundaries in modern frameworks