JavaScript queueMicrotask API Guide

The queueMicrotask function schedules a microtask to run before the next task in the event loop. Here's how to use it effectively.

Best Practices#

Use Cases:
✓ Batching multiple updates
✓ Deferring cleanup tasks
✓ Coalescing events
✓ Custom async primitives

Timing:
✓ Runs before next macrotask
✓ Same queue as Promise.then
✓ After current sync code
✓ Before requestAnimationFrame

Patterns:
✓ Schedule once, process many
✓ Store latest value
✓ Clear pending on flush
✓ Handle errors properly

Avoid:
✗ Long-running microtasks
✗ Infinite microtask loops
✗ Blocking the event loop
✗ Using when setTimeout suffices

queueMicrotask schedules functions to run in the microtask queue, after the current synchronous code but before the next macrotask (like setTimeout). Use it for batching updates, coalescing events, and creating custom async primitives. Microtasks run with higher priority than macrotasks, making them ideal for tasks that should complete before the browser renders or handles I/O. Be careful not to create infinite loops or block the event loop with long-running microtasks.

JavaScript queueMicrotask API Guide

Basic Usage#

Event Loop Order#

vs setTimeout#

Batching Updates#

State Synchronization#

Deferred Callbacks#

Custom Promise-like#

Event Coalescing#

DOM Update Batching#

Error Handling#

Comparison#

Best Practices#

Conclusion#

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