JavaScript visualisers

16 real-time visualisers. Each one is steppable and driven by your own input — not a recorded animation.

• Event Loop Simulator

  Watch the call stack, task queue and microtask queue take turns.

  event-loop · microtask

• Scope Chain Explorer

  See how a name is resolved outward through nested scopes.

  lexical-scope · shadowing

• Closure Inspector

  Which binding did each function actually capture?

  closure

• Hoisting & TDZ Timeline

  Step through the creation phase and the execution phase.

  hoisting · tdz

• this Binding Resolver

  Paste a call site, see which of the four rules fires.

  this-binding

• Prototype Chain Inspector

  Follow a property lookup up the chain until it is found.

  prototype · inheritance

• Memory & References

  Copy versus share, drawn as boxes and arrows.

  reference-vs-value

• Coercion Explorer

  Compare any two values and read the conversion steps.

  coercion · equality

• Array Method Lab

  Animate elements flowing through a map/filter/reduce chain.

  array-methods

• Iterator Stepper

  Pull values one at a time from an iterator or generator.

  iterator · generator

• Promise State Machine

  Pending to fulfilled or rejected, with handler queues.

  promise

• Async Waterfall

  Sequential awaits versus Promise.all, on a timeline.

  concurrency · async-await

• Proxy Trap Logger

  Every trap that fires, in the order it fires.

  proxy · reflect

• Regex Tester

  Live matches, capture groups and flags.

  regexp

• Complexity Playground

  Race real algorithms and watch the curves diverge.

  big-o · performance

• Event Flow Visualiser

  Capture, target and bubble phases through the DOM tree.

  events · delegation