What is an event listener in JavaScript?

An event listener in JavaScript is a procedure or function that waits for a specific event to occur on a designated element. When an event, such as a click, keypress, or mouse movement, takes place, the event listener acts as a handler that executes a callback function in response to that event. This mechanism allows developers to create interactive web applications by monitoring user actions and triggering specific responses.

For instance, if you attach an event listener to a button element, the function defined within the listener will run whenever the user clicks that button. This capability is central to JavaScript’s role in making web pages dynamic and responsive to user inputs.