What is the difference between the event loop and promises in JavaScript?

What is the difference between the event loop and promises in JavaScript?

The event loop is a mechanism that allows JavaScript to perform non-blocking I/O operations by offloading operations to the system. Promises, on the other hand, are objects that represent the eventual completion (or failure) of an asynchronous operation and its resulting value.

Can you explain how the event loop works in a bit more detail?

Sure! The event loop continuously checks the call stack and the message queue. If the call stack is empty, it takes the first message from the queue and pushes it onto the stack, allowing the associated callback to execute.

How do promises fit into the event loop?

Promises are executed in the microtask queue, which has a higher priority than the message queue. When a promise is resolved, its .then() callbacks are added to the microtask queue, which the event loop processes before moving on to the next message in the queue.

What happens if a promise is rejected?

If a promise is rejected, the error can be caught using the .catch() method. This callback is also added to the microtask queue, ensuring that it gets executed as soon as the current stack is clear.