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Learning Path

Async Output Basics

Understand why output order does not always match source order.

Step 1

Sync execution

Separate normal call stack work from queued work.

Step 2

setTimeout 0

See why 0ms does not mean immediate.

Step 3

Promise before timeout

Lock in the microtask-before-timer rule.

Step 4

Blocking loop delays timer

Understand why timers run late.