Zepto event.isPropagationStopped (v1.1+)

Event propagation is an important concept in JavaScript event handling. It refers to the way events are propagated or transmitted from one element to another in the DOM hierarchy. In some cases, you may want to prevent an event from propagating further up the hierarchy. This is where Event.isPropagationStopped() comes into play.

Event.isPropagationStopped() is a method provided by the Zepto JavaScript library for checking whether event propagation has been stopped. It returns a boolean value indicating whether or not the event's propagation has been stopped using the event.stopPropagation() method.

Usage

Here's an example of how to use Event.isPropagationStopped():

$(document).on('click', '#myLink', function(event) {
  event.stopPropagation();
  if (event.isPropagationStopped()) {
    console.log('Propagation has been stopped');
  }
});

In this example, we're attaching a click event handler to an element with ID "myLink". When the user clicks on the link, the event handler will be called. We're then calling event.stopPropagation() to stop the event from being propagated further up the DOM tree. Finally, we're using event.isPropagationStopped() to check whether the propagation has been stopped.

Deep Dive

Under the hood, Event.isPropagationStopped() simply checks whether the ._propagationStopped property of the event object is set to true. The ._propagationStopped property is an internal property of the event object that is set to true when event.stopPropagation() is called.

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Here's an example of Event.isPropagationStopped() being used internally by the trigger() method in Zepto. trigger() is a method that triggers the specified event on all elements in the set of matched elements.

Before triggering the event, trigger() checks whether the event's propagation has been stopped using event.isPropagationStopped(). If the propagation has been stopped, the method simply returns without triggering the event.

Conclusion

Event.isPropagationStopped() is a useful method provided by the Zepto JavaScript library for checking whether event propagation has been stopped. It can be used to prevent events from propagating further up the DOM tree, which can be useful in certain situations.

When using Event.isPropagationStopped(), it's important to remember that it simply checks whether the ._propagationStopped property of the event object is set to true. This property is an internal property of the event object that is set to true when event.stopPropagation() is called.

Overall, Event.isPropagationStopped() is a powerful tool that can be used to create more sophisticated and responsive web applications.

来源：JavaScript中文网 ，转载请注明来源 https://www.javascriptcn.com/post/4286