The JavaScript Event Loop: Asynchronicity on a Single Thread
The event loop is a queue that lets single-threaded JavaScript handle asynchronous tasks without blocking. It processes callbacks from Web APIs like `fetch` or `setTimeout` one at a time. The footgun: `setTimeout(fn, 0)` doesn't run instantly, just next.
The event loop is a queue that lets single-threaded JavaScript handle asynchronous tasks without blocking the main thread. It works with the call stack and a host environment (like a browser). Long-running operations like `fetch` are offloaded, and their callbacks are added to the queue to be executed once the stack is clear. The common footgun is assuming `setTimeout(fn, 0)` runs immediately; it only queues the function to run after the current synchronous code finishes.
Read the original → developer.mozilla.org
- #javascript
- #async
- #event loop
- #web apis
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