JavaScript Runtime and Closures

• A function remembers the variables around it from where it was created.
• JavaScript finishes the current work first before checking queued async work.
• Promise callbacks usually run before timer callbacks after the current code finishes.

Closures, lexical scope, event loop, microtasks, timers, promise ordering, and DOM callback behavior.

• Closure remembers definition scope.
• Stack first, microtasks second, next task after.
• Promises are microtasks.
• Busy JS blocks rendering too.

• Closures remember the lexical scope where a function was created, not where it was called.
• The event loop runs microtasks before the next macrotask after the current stack clears.
• Promise callbacks and timer callbacks differ in scheduling, which explains common interview output questions.
• Main-thread blocking affects not only code order but also responsiveness and rendering.

• Use the closure explanation when discussing custom hooks, event handlers, and stale state.
• Use microtask vs macrotask language in async output questions.
• Connect runtime behavior to browser performance, not only to console.log examples.