Which JS events will not bubble up?

In front-end development, event processing is a very critical link. When users interact with web pages, they often need to trigger corresponding operations and responses through events. Common events include mouse clicks, keyboard presses, and page loads. In the event delivery process, bubbling is an important mechanism that can deliver events from the bottom element to the top element. However, not all events have the characteristics of bubbling. This article will introduce some common JavaScript events that do not have bubbling delivery.

1. Focus and blur events:
   The focus event is triggered when an element gains focus, while the blur event is triggered when an element loses focus. These two events will not bubble up and will only be triggered on the current element. For example, when the user clicks on an input box, the focus event will be triggered on the input box without being passed to the parent element or other related elements.
2. Load and unload events:
   The load event is triggered after the page or image is loaded, and the unload event is triggered when the page is closed or jumped. These two events will not bubble up, they will only be triggered on the corresponding elements. For example, when the page completes loading, the load event fires on the window object and does not bubble up to other elements.
3. Scroll event:
   The scroll event is triggered when an element is scrolled, such as when scrolling a page in a browser or scrolling an element with a fixed size. This event will not bubble up, it will only fire on the scrolled element.
4. Input event:
   The input event is triggered when the user enters data or modifies the content of the input box. This event will not bubble up, it will only be triggered on the current input box. For example, in a form, when the user enters or deletes characters in an input box, the input event will be triggered on the input box without bubbling to other elements.
5. change event:
   The change event is triggered when the user changes the selection or input. It is often used for select elements or form elements such as input[type="radio"] and input[type="checkbox"]. This event will only be triggered on the changed element and will not bubble up to other elements.

It should be noted that the events listed above will not bubble and be delivered in all cases. Depending on the specific application scenarios and event binding methods, there may be some exceptions. In addition, by using event capture, you can also capture events that do not bubble up under certain circumstances.

In actual development, knowing which events will not bubble up is very important for correctly handling events. Sometimes, we may need to prevent the bubbling of events in the event handler, or achieve certain effects through a specific sequence of events. Therefore, understanding these events that are not delivered by bubbling can help us better understand and handle related interactive operations.

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