What events cannot be captured

Events that cannot be captured include scroll events, window events, focus events, input events and custom component events. Detailed introduction: 1. The scroll event is an event triggered when the user scrolls the web page. Due to the nature of scroll events, they cannot be processed in the event capture stage; 2. Window events refer to events related to the browser window, such as window resizing, closing, etc. These events are usually processed in the browser window itself, rather than Passed to the target element through the event stream; 3. Focus events refer to events triggered when an element gains or loses focus, etc.

The operating system for this tutorial: Windows 10 system, DELL G3 computer.

In the event model, some events cannot be captured. These events mainly fall into two categories: those that cannot be efficiently handled in the capture phase, and those that are not handled in the capture phase in accordance with their design intent. These events that cannot be captured are explained in detail below:

Scroll events: Scroll events are events that are triggered when the user scrolls the web page. Due to the nature of scroll events, they cannot be handled during the event capture phase. When the user scrolls the page, the browser needs to respond to the user's operations in the shortest possible time, so it is more suitable to handle the scroll event in the bubbling stage. Handling scroll events during the capture phase can cause delays in page rendering and a poor user experience.

Window events: Window events refer to events related to the browser window, such as window resizing, closing, etc. These events are typically handled within the browser window itself, rather than being passed through the event stream to the target element. Therefore, window events do not trigger the capture phase. Developers can bind window event handlers on the target element to respond to these events, but these handlers will not be executed during the capture phase.

Focus events (Focus events): Focus events refer to events that are triggered when an element gains or loses focus, such as focus and blur. These events are usually handled on the target element itself, rather than being passed to other elements through the event stream. Therefore, focus events do not trigger the capture phase. Developers can bind focus event handlers on the target element to respond to these events, but these handlers will not be executed during the capture phase.

Input events: Input events refer to events triggered when the user enters text in the input box, such as input and change. These events are usually handled within the input box itself, rather than being passed through the event stream to other elements. Therefore, input events do not trigger the capture phase. Developers can bind input event handlers on the target element to respond to these events, but these handlers will not be executed during the capture phase.

Custom component events: For custom components, the event handling method may be different from the event handling method of DOM elements. Events from custom components may not trigger the capture phase. Developers can bind corresponding event handlers on custom components to respond to these events, but these handlers will not be executed during the capture phase.

To sum up, the events that cannot be event captured mainly include scroll events, window events, focus events, input events and custom component events. Due to their own characteristics and the browser's processing mechanism, these events cannot be processed in the capture phase. However, developers can still handle these events at the target element or during the bubbling phase to meet actual needs.

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