问题
In the everyday front-end development I often use DOM as a global event bus that is accessible to every part of my client-side application.
But there is one "feature" in it, that can be considered harmful, in my opinion: any listener can prevent propagation of an event emitted via this "bus".
So, I'm wondering, when this feature can be helpful. Is it wise to allow one listener to "disable" all the other? What if that listener does not have all information needed to make right decision about such action?
Upd
This is not a question about "what is bubbling and capturing", or "how Event.stopPropagation actually works". This is question about "Is this good solution, to allow any subscriber to affect an event flow"?
回答1:
We need (I am talking about current usage in JS) stopPropagation() when we want to prevent listeners to interfere with each other. However, it is not mandatory to do so.
Actual reasons to avoid stopPropagation:
Using it usually means that you are aware of code waiting for the same event, and interfering with what the current listener does. If it is the case, then there may (see below) be a design problem here. We try to avoid managing a single thing at multiple different places.
There may be other listeners waiting for the same type of event, while not interfering with what the current listener does. In this case,
stopPropagation()may become a problem.
But let's say that you put a magic listener on a container-element, fired on every click to perform some magic. The magic listener only knows about magic, not about the document (at least not before its magic). It does one thing. In this case, it is a good design choice to leave it knowing only magic.
If one day you need to prevent clicks in a particular zone from firing this magic, as it is bad to expose document-specific distinctions to the magic listener, then it is wise to prevent propagation elsewhere.
An even better solution though might be (I think) to have a single listener which decides if it needs to call the magic function or not, instead of the magic function being a stoppable listener. This way you keep a clean logic while exposing nothing.
To provide (I am talking about API design) a way for subscribers to affect the flow is not wrong; it depends on the needs behing this feature. It might be useful to the developers using it. For example, stopPropagation has been (and is) quite useful for lots of people.
Some systems implement a continueX method instead of stopX. In JavaScript, it is very useful when the callees may perform some asynchronous processing like an AJA* request. However, it is not appliable to the DOM, as the DOM needs results in time. I see stopPropagation as a clever design choice for the DOM API.
来源：https://stackoverflow.com/questions/37698246/why-do-we-need-event-stoppropagation-in-dom-is-it-bad-architectural-pattern