Event bubbling is a relatively simple concept controlling how JS events occur on the DOM.
Let's say a user clicks a paragraph tag. This would trigger any
onclick events on that paragraph tag. Regardless of if there are any or not, the event will then "bubble up" to all the parent elements. It would check if there's any
onclick elements for the surrounding
article tag, the
div tag around that, all the way until it reaches the top of the DOM.
As the event moves up the DOM, the range of elements it looks at expands, like a bubble getting larger. Hence the name "event bubbling!"
Why Event Bubbling? #
onclick event on a wrapper element, you're rarely ever clicking on the wrapper element itself. Most likely you're clicking on elements inside the wrapper.
Event bubbling makes it so clicking on elements inside the wrapper still triggers the wrapper's own event. Clicking on a paragraph in the wrapper will do nothing, but once it bubbles up to the wrapper itself, it will see it has its own
onclick event and set it off.
Find the Starting Element #
If you want to see the element that set off the event bubbling, use
event.target. Every event function has an
event object with info from the browser, and
event.target is the element the event originated from.
This helps if you need to track what element inside that wrapper triggered the event. This context could change what you want the function to be, or if you want to run it at all.
Speaking of which...
Stop the Bubbling! #
Want to keep an event from bubbling up? The
event object also has a function called
event.stopPropagation() which will keep the event from moving further up the DOM.