eleven.eight The value of this while using the addEventListener()

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eleven.eight The value of this while using the addEventListener()

Inside guide I use the fresh new dispute label experiences to help you reference case object. In reality you need to use people name you adore as well as quite normal to see e or evt.

The value of this inside of the event listener function passed to the addEventListener() method will be a reference to the node or object the event is attached too. In the code below I attach an event to a

and then using this inside of the event listener gain access to the

element the event is attached too.

When events are invoked as part of the event flow the this value will remain the value of the node or object that the event listener is attached too. In the code below we add a click event listener to the and regardless of if you click on the

or the the value of this always points to .

As well its potential making use of the knowledge.currentTarget property to obtain the exact same reference, for the node or object invoking the function listener, that so it assets provides. Regarding password lower than We control case.currentTarget experience object assets showcasing which efficiency a comparable worthy of because this.

eleven.8 Referencing the mark of a meeting rather than the fresh node or target the event was invoked for the

Because of the event flow its possible to click a

, contained inside of a element and have a click event listener attached to the element get invoked. When this happens, the event object passed to the event listener function attached to the provides a reference (i.e. event.target) to the node or object that the event originated on (i.e. the target). In the code below when the

is clicked, the element’s click event listener is invoked and the event.target property references the orginal

that was the target of the click event. The event.target can be extremely useful when an event that fires because of the event flow needs knowledge about the origin of the event.

Consider that in our code example if the element is clicked instead of the

then the event target and the element node that the event listener is invoked on are the same. Therefore event.target, this, and event.currentTarget will all contain a reference to the element.

eleven.9 Cancelling standard web browser situations having fun with preventDefault()

Browsers provide several events already wired up when an HTML page is presented to a user. For example, clicking a link has a corresponding event (i.e. you navigate to a url). So does clicking a checkbox (i.e. box is checked) or typing text into a text field (i.e. text is inputed and appears on screen). These browser events can be prevented by calling the preventDefault() method inside of the event handler function associated with a node or object that invokes a browser default event. In the code below I prevent the default event that occurs on a , , and