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Leonard Ginters
Leonard Ginters

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The JavaScript event loop execution order, summarized in a simple manner

The simplified order

  1. Everything in sync
  2. Microtask queue
  3. Task queue

Real-world examples


setTimeout, setInterval, setImmediate, ...


Promises, queueMicrotask, MutationObserver, ...

Everything combined

// Schedules a new microtask
queueMicrotask(() => console.log("microtask"));

// Schedules a new task
setTimeout(() => console.log("task"), 0);

// Output order: main, microtask, task
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Please note that this describes a really, really simplified perfect-world case. If you would like to find out more, I can highly recommend Jake Archibald's blog post on this topic.

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