Prevent Event Propagation with JS

TODO: collapasable, copyable, download, etc

I have a link. In JS in the event handler, I call event.preventDefault(), however, I see the parent div which also has an onClick handler getting executed. What is going on?In JavaScript, when you have nested elements with event handlers, and you trigger an event on a child element, the event can propagate up to the parent elements. This is known as event bubbling.

When you call event.preventDefault() in your event handler, it prevents the default action of the event (e.g., following a link), but it does not stop the event from bubbling up to parent elements. If the parent div has its own onClick handler, that handler will be executed unless you explicitly stop the event from bubbling.

To stop the event from propagating to parent elements, you should use event.stopPropagation(). This method prevents further propagation of the current event in the capturing and bubbling phases.

Here is an example of how you might use both event.preventDefault() and event.stopPropagation():

childElement.addEventListener('click', function(event) {
    event.preventDefault();    // Prevent default action (like following a link)
    event.stopPropagation();   // Stop the event from bubbling up to parent elements
    // Your code here
});

By using both methods, you can prevent the default action of the event and also stop it from triggering event handlers on parent elements.Do you need both? Will stopPropagation prevent the default actions as well?No, event.stopPropagation() and event.preventDefault() serve two different purposes, and using stopPropagation() does not prevent the default action of the event.

• event.stopPropagation(): This method is used to stop the event from bubbling up the DOM tree, preventing any parent handlers from being notified of the event. It's used when you want to isolate an event to a specific element and ensure it doesn't trigger event handlers on parent elements.

• event.preventDefault(): This method prevents the default action the browser makes on that event. For instance, clicking a link normally takes you to a new page, and event.preventDefault() will stop that from happening.

If you want to both prevent the default action and stop the event from bubbling up, you need to call both methods in your event handler:

element.addEventListener('click', function(event) {
    event.preventDefault();  // Prevent the default action
    event.stopPropagation(); // Stop the event from bubbling up
    // Additional code
});

If your goal is only to stop the default action (like following a link), event.preventDefault() is sufficient. If you also want to prevent parent elements from handling the same event, you should use event.stopPropagation() in addition to event.preventDefault().Intead of stopPropagation, in the outer div, how would I detect if the user had clicked on this div or if instead, the event was bubbled up and propagated? I would like to filter out the propagations To distinguish between a direct click on an element and an event that bubbled up from a child element, you can compare the event.target with event.currentTarget within the event handler of the outer div.

• event.target: This is the element that triggered the event, i.e., the element on which the event originally occurred.

• event.currentTarget: This is the element that the event listener is actually attached to. When you're inside an event handler, event.currentTarget is the element to which the event handler is bound.

In the case of an event that bubbles up, event.target will be the child element where the event originated, and event.currentTarget will be the element (in your case, the outer div) where the listener is attached.

Here's an example of how you can use this in your code:

outerDiv.addEventListener('click', function(event) {
    if (event.target === event.currentTarget) {
        // The click occurred directly on the outer div
        console.log('Clicked directly on the outer div');
    } else {
        // The click bubbled up from a child element
        console.log('Click bubbled up from a child element');
    }
});

In this example, if a user clicks directly on the outer div, both event.target and event.currentTarget will be the same (the outer div). However, if the click event originated from a child element and bubbled up, event.target will be the child element, and event.currentTarget will still be the outer div. This allows you to differentiate between a direct click and a bubbled event.

Prevent Event Propagation with JS created at Tue Jan 20 1970 17:32:18 GMT+0000 (Coordinated Universal Time)