JavaScript Events and Methods Quiz
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Questions and Answers

What does the preventDefault() method do?

  • It refreshes the page.
  • It stops the default behavior of the element on which the event was triggered. (correct)
  • It initiates the default behavior of the event.
  • It adds a new event listener.
  • The preventDefault() method can be invoked on any JavaScript object.

    False

    Why is it important to include a page in the href attribute even when using JavaScript?

    For accessibility reasons.

    The method _____ can be used to prevent the default action of a click event.

    <p>preventDefault</p> Signup and view all the answers

    Match the following events with their default behaviors:

    <p>Click on a link = Navigates to a new page Form submission = Sends data to a server Refresh button = Reloads the current page Checkbox toggle = Changes the checkbox state</p> Signup and view all the answers

    What does e.target represent in an event?

    <p>The element that originated the event</p> Signup and view all the answers

    E.currentTarget refers to the element that originated the event.

    <p>False</p> Signup and view all the answers

    What function is called when the anchor element is clicked in the provided code?

    <p>doSomething</p> Signup and view all the answers

    In the event handler, e.preventDefault() is used to prevent the ______ action.

    <p>default</p> Signup and view all the answers

    Match the following terms with their descriptions:

    <p>e.target = Element that originated the event e.currentTarget = Element with the event handler bound init = Function called once DOM is fully loaded doSomething = Function executed on event trigger</p> Signup and view all the answers

    What is the recommended method to bind events to an element?

    <p>.addEventListener()</p> Signup and view all the answers

    It is acceptable to hard-code all lost events in a project.

    <p>False</p> Signup and view all the answers

    What should you do to initiate event binding after the DOM has loaded?

    <p>Use document.addEventListener('DOMContentLoaded', init);</p> Signup and view all the answers

    When binding an event, it is essential to know what type of event is being __________.

    <p>triggered</p> Signup and view all the answers

    Match the following event questions to their purpose:

    <p>Which element triggers the event? = Identifies the source of the event What type of event is it? = Specifies the event action What needs to happen when the event occurs? = Defines the event handler function</p> Signup and view all the answers

    Which element is used to trigger an event in the example?

    <p>#shoppingcart</p> Signup and view all the answers

    Event delegation is a good practice when handling events in JavaScript.

    <p>True</p> Signup and view all the answers

    What is the first step in the two-step process after the DOM has loaded?

    <p>Wait until the DOM tree has loaded in-memory.</p> Signup and view all the answers

    Which of the following methods can be used to access data attributes in JavaScript?

    <p>getAttribute()</p> Signup and view all the answers

    An arrow function can only be used when a function does not require any parameters.

    <p>False</p> Signup and view all the answers

    What is the purpose of the 'dataset' property in JavaScript?

    <p>To access data attributes directly using the dataset collection.</p> Signup and view all the answers

    In JavaScript, an anonymous function can be written as _____(a) => a + 100;

    <p>arrow</p> Signup and view all the answers

    Match the following JavaScript function types with their descriptions:

    <p>Anonymous function = Does not have a name and can be defined on the fly Named function = Regular function declaration with a name Arrow function = Shorter syntax for writing functions, defined with =&gt; Function expression = A function defined within an expression context</p> Signup and view all the answers

    When should you preferably use a named function?

    <p>When the function is complex and needs to be reused</p> Signup and view all the answers

    The following is an example of a valid anonymous function: function showMessage(e) {}

    <p>False</p> Signup and view all the answers

    How do you add a click event listener to a button element in JavaScript?

    <p>Use document.querySelector('button').addEventListener('click', function() {});</p> Signup and view all the answers

    What happens when stopImmediatePropagation() is called during an event?

    <p>No remaining listeners will be called.</p> Signup and view all the answers

    Event capturing fires on the innermost element first.

    <p>False</p> Signup and view all the answers

    What parameter must be added to the addEventListener() method to enable event capturing?

    <p>true</p> Signup and view all the answers

    In event capturing, the event propagates from the ______ to the child.

    <p>parent</p> Signup and view all the answers

    Match the method with its function:

    <p>stopPropagation() = Prevents further propagation of the current event stopImmediatePropagation() = Halts all remaining listeners for the current event addEventListener() = Attaches an event handler to an element preventDefault() = Prevents the default action of an event</p> Signup and view all the answers

    What is a key consideration when implementing event capturing?

    <p>Clearly state why capturing is used instead of bubbling.</p> Signup and view all the answers

    Listeners of the same type can fire on parent elements when stopPropagation() is called.

    <p>False</p> Signup and view all the answers

    Describe a potential downside of using event capturing indiscriminately.

    <p>It can confuse developers due to reversed event flow.</p> Signup and view all the answers

    Which type of function is recommended for reuse and legibility in most cases?

    <p>Named function</p> Signup and view all the answers

    Arrow functions can be used when the name of the function is deemed unnecessary.

    <p>True</p> Signup and view all the answers

    When would you prefer using the close method in DOM manipulation?

    <p>When you need to traverse the DOM tree upwards to find the nearest matching parent.</p> Signup and view all the answers

    You can dynamically add items to a list using the event object property, ___ .

    <p>e.target</p> Signup and view all the answers

    What is the key takeaway for deciding when to use a named versus an anonymous function?

    <p>Use named functions for reuse and clarity, and anonymous for one-off functions.</p> Signup and view all the answers

    Using the parentNode property is favored over the closest function for DOM traversal.

    <p>False</p> Signup and view all the answers

    What does the closest function do?

    <p>Travels up the DOM tree to find the nearest parent matching a specified selector.</p> Signup and view all the answers

    Study Notes

    Event Bubbling

    • Event bubbling is a propagation method where an event, triggered on an inner element, successively moves up the DOM tree to its parent elements.
    • This propagates to all ancestors until the root element.

    Event Capturing

    • Event capturing is the opposite of bubbling.
    • Events start at the parent and move down successively through the child elements until the innermost element.
    • It's useful when needing to handle events on multiple nested elements in a specific order.

    Stop Propagation

    • Prevents further propagation of the current event throughout the DOM tree.
    • It doesn't prevent default behaviors from occuring.

    Stop Immediate Propagation

    • Prevents further propagation of the event to other listeners on the same element, even along any ancestral line.

    Event Object

    • Every event handler automatically receives an event object.
    • This object holds relevant information such as the event's origin, its parent, and coordinates.

    PreventDefault()

    • This method helps stop the default behavior of an HTML element.
    • It's crucial for handling events that would otherwise cause unwanted defaults, like page reloads or form submissions.

    DOM Element Selection

    • document.querySelector() selects only the first matching element.
    • document.querySelectorAll() returns all elements matching a given selector.

    Dynamic Data and Event Handlers

    • Dynamically added elements will not have associated event handlers anymore.
    • Event delegation is the solution to this problem.

    Event Delegation

    • Event delegation is a technique where event handlers are attached to a parent element rather than to individual child elements, so it can handle events that are triggered on new elements, ensuring they continue to be handled correctly.

    Static vs Dynamic Data

    • Static data is predefined HTML content.
    • Dynamic data is updated or inserted based on external information, for example through an API.

    Iterations with JavaScript

    • JavaScript offers several built-in functions that iterate over arrays. Using a forEach() , or for...of loop is preferred over a simple for loop.

    Function Reusability

    • Functions improve code reusability by enabling the same block of code to be executed at various points.

    Function Call

    • Calling a function starts its execution.
    • The values written within the function body modify the arguments to the function.

    Function Parameters

    • Values passed to functions are called parameters or arguments.
    • Modifying variable values within a function won't modify the original variables outside the function.

    Event Handling

    • e.preventDefault() method stops the default behavior of an event.
    • This is ideal when you want to prevent a default action—such as a page reload—associated with a specific event, like a form submission or a link click, without interfering with other handlers.

    Event Properties

    • e.target retrieves the exact element that triggered the event and the e.currentTarget is the element the event listener is tied to.

    DOM Scripting

    • DOM scripting is the use of JavaScript to modify or access HTML elements.

    HTML Data Attributes

    • HTML data attributes are used to store custom data linked to HTML elements.

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    Description

    Test your knowledge on JavaScript event handling and methods like preventDefault(). This quiz covers essential concepts such as event binding, default behaviors, and key event properties. Perfect for those looking to deepen their understanding of JavaScript interactions.

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