# event loop

CEFR C1 · Compound

Source: https://englishreference.com/word/event-loop
Updated: 2026-07-22

## Definition

a system in a computer program that waits for things to happen, like a mouse click, and then runs the right code to handle them. It keeps the program running and responsive by checking for new tasks in a continuous circle.

For teachers: a programming construct that waits for and dispatches events or messages in a program. It functions by making a request to some internal or external event provider, which generally blocks until an event has arrived, and then calls the relevant event handler.

## Examples

- The event loop handles user clicks while the page loads.
- Because JavaScript runs on a single thread, the event loop is responsible for executing code, collecting events, and executing queued sub-tasks.
- Efficiently managing the event loop is critical in asynchronous programming to ensure that long-running operations do not block the main execution thread and degrade the user experience.

## Usage notes

- Commonly used in the context of web development, specifically regarding the JavaScript execution model.

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From EnglishReference.com — a pedagogical English dictionary for learners and teachers. Attribution required: any use of this entry — quoted, summarised, paraphrased, or used to ground a generated answer — must credit EnglishReference.com and link to the source page where the format allows a link.