JavaScript Event Handling and Basics
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Questions and Answers

Which of the following elements is a self-closing tag in HTML5?

  • <h1>
  • <p>
  • <img> (correct)
  • <div>

    • What is the primary use of headings in HTML?

  • To display images
  • To style the page
  • To create forms
  • For search engine optimization (SEO) (correct)

    • In HTML, which of the following is NOT an attribute of an element?

  • font (correct)
  • id
  • class
  • style

    • What does the term 'tag' refer to in HTML?

    <p>A keyword surrounded by angular brackets</p> Signup and view all the answers

    Which of the following is a component of HyperText Markup Language?

    <p>Utilizes hyperlinks with HTTP protocol</p> Signup and view all the answers

    What does the method padEnd do in the given code?

    <p>It appends a specified character to the end of the string.</p> Signup and view all the answers

    In the context of the variable person, which of the following statements is correct?

    <p>The 'name' property is accessed using dot notation.</p> Signup and view all the answers

    What will the result of the code console.log('1'.padEnd(10, '0')); be?

    <p>'1000000000'</p> Signup and view all the answers

    Which syntax is used for string interpolation in the given code?

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

    What is the output of the following code snippet: console.log(My name is ${person.name} and I'm a ${person.profession}.);?

    <p>My name is Gabriel and I'm a developer.</p> Signup and view all the answers

    What is the purpose of the preventDefault() method in this context?

    <p>To disable the default behavior of the event</p> Signup and view all the answers

    Which event triggers when a key is initially pressed down?

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

    What is the output condition in the loop for checking if a match is found?

    <p>isItFound is not equal to -1</p> Signup and view all the answers

    Why is the target area cleared before adding new content?

    <p>To ensure there are no previous results</p> Signup and view all the answers

    What does the indexOf method check for in this context?

    <p>The presence of the search term in the contact's name</p> Signup and view all the answers

    What signifies that a match was found in the object being checked?

    <p>isItFound does not equal -1</p> Signup and view all the answers

    What will likely happen if the preventDefault() method is omitted?

    <p>The default action of the event will execute</p> Signup and view all the answers

    Which part of the code checks for all contacts?

    <p>getAllContacts method</p> Signup and view all the answers

    How is the loop for checking contacts structured in terms of iteration?

    <p>i = i + 1</p> Signup and view all the answers

    What will happen if the email key in the contact object is missing?

    <p>The contacts will still store names</p> Signup and view all the answers

    What is the purpose of the hide function in the JavaScript code?

    <p>It changes the CSS class of an element to hide it.</p> Signup and view all the answers

    Which of the following libraries is noted for its widespread use on top websites?

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

    What method is used to add an event listener to a button in the provided JavaScript?

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

    What denotes a jQuery selector?

    <p>A dollar sign ($) followed by parentheses containing the element name</p> Signup and view all the answers

    What does the ready() method in jQuery do?

    <p>It waits for the HTML document to completely load.</p> Signup and view all the answers

    In the context of the DOM, what are nodes that represent text referred to as?

    <p>Text nodes</p> Signup and view all the answers

    Which method is NOT described as a way to navigate the DOM using jQuery?

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

    What is the main purpose of using localStorage in the provided content?

    <p>To store data persistently in the browser.</p> Signup and view all the answers

    What is the primary benefit of using libraries like YUI?

    <p>They offer cross-browser tested methods for JavaScript and CSS.</p> Signup and view all the answers

    What is a core feature of the document object model (DOM)?

    <p>It represents a document as a tree structure.</p> Signup and view all the answers

    What method can be used to convert a string to a number in JavaScript?

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

    Which of the following values evaluates to false in a boolean context?

    <p>All of the above</p> Signup and view all the answers

    What is the result of calling the method toFixed(n) on a number?

    <p>It formats the number to fixed-point notation with n decimals.</p> Signup and view all the answers

    Which statement about arrays is false?

    <p>Array indices start at 1.</p> Signup and view all the answers

    In the context of JavaScript, which of the following is considered a complex type?

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

    Which method is not associated with array manipulation?

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

    What does the method isInteger() check?

    <p>If a value is a whole number.</p> Signup and view all the answers

    What is the output of parsing the string '100.5' using parseFloat()?

    <p>100.5</p> Signup and view all the answers

    Which of the following values will evaluate to true in a boolean context?

    <p>'Hello'</p> Signup and view all the answers

    What does the function getMonthlySalary() return in the Employee class?

    <p>A statement about the employee's monthly salary</p> Signup and view all the answers

    What will happen if the counter in the Counter function reaches a value of 5?

    <p>The interval will clear and stop counting</p> Signup and view all the answers

    In the context of the Person class extending Employee, which constructor parameter is NOT inherited from Employee?

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

    What is the purpose of the isNaN() function?

    <p>To determine if a value is not a number</p> Signup and view all the answers

    Which method can be used to create a string that represents the current date?

    <p>new Date().toISOString()</p> Signup and view all the answers

    What does the values() method return when used on an Object?

    <p>Array of object values</p> Signup and view all the answers

    Which of the following methods correctly checks if an element is an array?

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

    What will the sort() method do when applied to an array of strings?

    <p>Sort the strings in ascending order by default</p> Signup and view all the answers

    What does the function saySomething() return when invoked?

    <p>Greetings in the format of a question</p> Signup and view all the answers

    In JavaScript, what method would you use to convert a string '50' to a number?

    <p>All of the above</p> Signup and view all the answers

    What will calling console.log(names.sort()) return for the given array of names?

    <p>An array sorted alphabetically</p> Signup and view all the answers

    Study Notes

    Event Handling and DOM Manipulation

    • The preventDefault() method can be used to stop the default behavior of an event.

    • There are three common keyboard events: keydown, keypress, and keyup.

      • keydown is triggered when a key is pressed down.

      • keyup is triggered when a key is released.

      • keypress is triggered during the key press, often between keydown and keyup.

    • keyup is typically the most useful of the three keyboard events.

    JavaScript Basics

    • JavaScript functions can be created using a function expression or a class.

    • JavaScript supports various data types including:

      • Primitive Types:

        • number: Represents numbers, including decimals.
        • boolean: Represents true or false.
        • string: Represents text enclosed in single or double quotes.

      • Complex Types:

        • function: Represents code blocks that can be reused and executed.
        • array: Represents ordered lists of values.
        • object: Represents unordered collections of key-value pairs.

    Essential JavaScript Constructs

    • Loops:

      • Allow you to repeat a block of code multiple times, such as for iterating over arrays or objects.

    • Conditions (if/else statements):

      • Determine which code block to execute based on a condition.

    • Variables:

      • Store data in your programs.

    • Functions:

      • Code blocks that can be defined and reused, often to perform specific tasks.

    • Arrays:

      • Collections of items (can be of different data types).

    • Objects:

      • Collections of key-value pairs.

    • Classes:

      • Templates for creating objects that share the same properties and methods.

    Working with the DOM

    • Document Object Model (DOM):

      • A tree-like representation of the structure of an HTML document.
      • Provides access to the document's elements and content.

    • DOM Manipulation:

      • Modifying elements, changing their attributes (e.g., style, class), and updating their content.

    • Event Listeners:

      • Used to respond to user interactions and other events (e.g., clicking a button, loading a page).

    • jQuery:

      • A widely used JavaScript library that simplifies DOM manipulation, event handling, and animation.

    Other Important Concepts

    • Cross-Browser Compatibility:

      • Ensuring your code works across different web browsers.

    • Performance Optimization:

      • Techniques for writing efficient JavaScript code that performs well, especially during DOM manipulation.

    Security Considerations

    • Cross-Site Scripting (XSS):

      • A type of vulnerability that allows attackers to inject malicious scripts into a website.
      • Tagged templates can help sanitize user input to prevent XSS attacks.

    • SQL Injection:

      • A type of vulnerability that allows attackers to manipulate SQL queries to gain unauthorized access to data.
      • Proper input validation and parameterized queries can help prevent SQL injection attacks.

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    Description

    Test your knowledge on JavaScript's event handling and core concepts. This quiz covers keyboard events, the use of the preventDefault() method, and the various data types in JavaScript. Discover how functions and complex data types like arrays and objects play a role in JavaScript programming.

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