The event loop enables JavaScript's asynchronous, non-blocking behavior. Here's how it works.
The Basics
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Call Stack
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Task Queue (Macrotasks)
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Microtask Queue
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Execution Order
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Async/Await Behavior
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Blocking the Event Loop
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requestAnimationFrame
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Node.js Specifics
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Common Pitfalls
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Debugging Tips
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Best Practices
Performance:
✓ Avoid blocking synchronous code
✓ Break up heavy computation
✓ Use Web Workers for CPU-intensive tasks
✓ Batch DOM updates
Understanding:
✓ Microtasks run to completion
✓ One macrotask per iteration
✓ rAF before repaint
✓ await creates microtask boundaries
Patterns:
✓ Use queueMicrotask for urgent async
✓ Use setTimeout(fn, 0) to yield
✓ Use requestIdleCallback for low priority
✓ Use rAF for animations
Debugging:
✓ Console.log execution order
✓ Use browser performance tools
✓ Check for stack traces
✓ Monitor event loop lag
Conclusion
The event loop enables asynchronous JavaScript through task queues. Synchronous code runs first, then all microtasks, then one macrotask, then render if needed. Understanding this helps write performant, non-blocking code and debug timing issues.