Why do you need to remove addEventListener after using it in JS?

In JavaScript, adding event listeners is a common operation. You can use the addEventListener method to add event listeners. However, in some cases, the event listener is removed in time after the event is triggered. This is usually for the following reasons:

1. Avoid memory leaks: In JavaScript, if an object is referenced but no longer used, it still takes up memory. If we add a lot of event listeners and do not remove them in time, these event listeners will continue to occupy memory and cause memory leaks.

2. Avoid triggering events repeatedly: Some events may be triggered multiple times, such as the scroll event. If we don't remove the event listener, the event handler will be executed every time the event is fired. This may cause problems or poor performance in the program.

3. Change element state: Certain events change the state of an element, such as the mouseover and mouseout events. If we do not remove these event listeners in time, they will keep changing the element state, resulting in a poor user experience.

Therefore, after using the addEventListener method to add an event listener, we usually need to use the removeEventListener method to remove the event listener when it is not needed. Remove to avoid the above problems. At the same time, we can also use some tools to assist in the management of event listeners, such as event delegation, event proxies, etc.