11.eight The value of that it while using the addEventListener()

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11.eight The value of that it while using the addEventListener()

Contained in this publication I use the brand new conflict title feel to help you reference the big event object. In reality you should use any term you adore and its particular quite normal observe e otherwise evt.

The value of this inside of the event listener function passed to the addEventListener() method will be a reference to the node free dating sites for Professional Sites 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 .

On top of that its likely utilising the feel.currentTarget possessions to obtain the same resource, to your node otherwise target invoking the event listener, that the that it property brings. In the code lower than We leverage case.currentTarget experience object assets exhibiting this efficiency a similar really worth as this.

eleven.8 Referencing the goal out-of an event and not the brand new node otherwise target case was invoked to your

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.nine Cancelling standard browser incidents playing 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