When a W3C event listener’s event occurs and it calls its associated function, it also passes a single argument to the function—a reference to the event object. The event object contains a number of properties that describe the event that occurred.
Event handlers can be used to handle, and verify, user input, user actions, and browser actions:
- Things that should be done every time a page loads.
- Things that should be done when the page is closed.
- Action that should be performed when a user clicks a button.
- Content that should be verified when a user inputs data.
The parameter e that you are asking about is an Event object, and it represents the event being fired which caused your function to be executed. It doesnt really have to be e , you can name it anything you want just like all other function parameters.
Definition and Usage. The target event property returns the element that triggered the event. The target property gets the element on which the event originally occurred, opposed to the currentTarget property, which always refers to the element whose event listener triggered the event.
What is an event object?
An event listener is an object that “listens” for events from a GUI component, like a button. When the user generates an event, the system creates an event object which is then sent to the listener that has been registered for the GUI component. … Then, a method in the listener object is invoked.
Event bubbling directs an event to its intended target, it works like this: A button is clicked and the event is directed to the button. … If no event handler is set for that object, the event bubbles up (like a bubble in water) to the objects parent.
What is an event?
noun. something that happens or is regarded as happening; an occurrence, especially one of some importance. the outcome, issue, or result of anything: The venture had no successful event. something that occurs in a certain place during a particular interval of time.
How does an event listener work?
An event listener is like an ear waiting for a message. When the event occurs, the subroutine chosen as event listener works using the event arguments. There are always two important data: the moment where the event happens and the object where this event occurs. Other argument are more data about what’s happened.
Is Onclick an event listener?
While onclick works in all browsers, addEventListener does not work in older versions of Internet Explorer, which uses attachEvent instead. The downside of onclick is that there can only be one event handler, while the other two will fire all registered callbacks.
What is the role of event listeners in event handling?
Event listeners represent the interfaces responsible to handle events. … Every method of an event listener method has a single argument as an object which is the subclass of EventObject class. For example, mouse event listener methods will accept instance of MouseEvent, where MouseEvent derives from EventObject.
How do I remove event listener?
The removeEventListener() method removes an event handler that has been attached with the addEventListener() method. Note: To remove event handlers, the function specified with the addEventListener() method must be an external function, like in the example above (myFunction).
Event capturing is the event starts from top element to the target element. It is the opposite of Event bubbling, which starts from target element to the top element.
What is an event parameter?
Events and parameters describe the action a user completes along with the data in the action. An event is the action that the user completes and the parameters for the event contain the data associated with that event.