Modern JavaScript: Classes and DOM Manipulation

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Questions and Answers

Which keyword is specifically designated for creating a class in JavaScript?

  • object
  • class (correct)
  • function
  • define

What is the primary function of the constructor() method within a JavaScript class?

  • To set up the initial state of the object when a new instance of the class is created. (correct)
  • To destroy the class instance and release memory.
  • To manage inheritance and extend properties from parent classes.
  • To define static methods that are accessible without instantiating the class.

What keyword is utilized in JavaScript to enable a class to inherit properties and methods from another class?

  • implements
  • extends (correct)
  • super
  • inherit

Which method is correctly used to dynamically insert HTML elements into the DOM?

<p>appendChild() (D)</p>
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Inside a class method, how do you ensure that this correctly refers to the class instance within an event listener?

<p><code>method.bind(this)</code> (B)</p>
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Which object in the browser environment represents the entire web page currently loaded?

<p>document (C)</p>
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Which method is the proper way to attach a new event listener to a specified DOM element?

<p>addEventListener() (B)</p>
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In JavaScript, what is the data type of null?

<p>object (C)</p>
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What is the role of super() when called inside a class constructor?

<p>It invokes the constructor of the parent class. (B)</p>
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Which property accurately retrieves all child nodes of a specified DOM element, including text and comment nodes?

<p>childNodes (A)</p>
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How are almost all entities regarded in JavaScript's conceptual framework?

<p>an object (C)</p>
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Which storage option in a browser is designed to retain data even after the browser is closed and reopened?

<p>localStorage (D)</p>
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What specific result does the querySelector() method provide when searching the DOM?

<p>Only the very first element that matches the specified selector. (C)</p>
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As of ES2022+, which symbol is designated for declaring a private field within a JavaScript class?

<h1>(D)</h1>
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In event handling, what is the primary effect of calling e.preventDefault() on an event object?

<p>It prevents the browser from carrying out the event's default action. (A)</p>
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Which method or property should you use to modify the text content of a DOM element?

<p>All of the above (D)</p>
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What does DOM stand for in the context of web development?

<p>Document Object Model (C)</p>
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In which scenario is JSON.stringify() typically used?

<p>To transform a JavaScript object into a JSON string. (C)</p>
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What concept does 'lexical scoping' refer to in JavaScript?

<p>Scope determined by the location of variable declarations in the source code (D)</p>
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Which method is correctly used to detach an event listener that was previously added to an element?

<p>removeEventListener() (C)</p>
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Flashcards

What is the keyword to create a class in JavaScript?

Keyword used to create a class.

What does constructor() do?

Initializes a newly created object from a class.

What keyword inherits a class?

Keyword to inherit properties from another class.

What method adds DOM elements?

Method to add a DOM element dynamically.

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How to bind 'this' in a class method?

Binds 'this' inside an event listener in a class method.

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What object represents the web page?

The object that represents the web page in the browser.

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How to add an event listener?

Method used to add an event listener to an element.

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What is typeof null?

Returns 'object'.

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What is the purpose of super()?

Refers to the parent class constructor.

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How to get all child nodes?

Returns all child nodes of an element.

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Everything in JavaScript is...

An object.

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Local Storage usage?

Allows persistent data storage in the browser.

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What does querySelector() return?

Returns the first matching element.

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What symbol defines a private class field?

Symbol to define a private field in a JavaScript class (ES2022+).

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What does e.preventDefault() do?

Prevents the default action of the event.

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How to update the text of a DOM element?

querySelectorAll.

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What is the DOM?

Stands for Document Object Model.

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When do you use JSON.stringify()?

To converts a JavaScript object to a JSON string.

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What is lexical scoping?

Scope based on location in source code.

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How to remove an event listener?

Method used to remove an event listener.

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Study Notes

  • class keyword creates a class in JavaScript.
  • constructor() method initializes a class.
  • extends keyword inherits a class in JavaScript.
  • appendChild() method dynamically adds a DOM element.
  • method.bind(this) correctly binds this inside an event listener in a class method.
  • document object represents the web page loaded in the browser.
  • addEventListener() method adds an event listener to an element.
  • The output of typeof null in JavaScript is object.
  • super() in a constructor refers to the parent class.
  • childNodes property returns all child nodes of an element.
  • In JavaScript, everything is an object.
  • localStorage mechanism enables persistent data storage in the browser.
  • querySelector() method returns the first matching element.
  • # symbol defines a private field in a JavaScript class (ES2022+).
  • e.preventDefault() prevents the default action of an event in an event handler.
  • innerText, textContent, and innerHTML methods update the text of a DOM element.
  • DOM is the Document Object Model.
  • JSON.stringify() converts an object into a JSON string.
  • Lexical scoping is scope based on location in source code.
  • removeEventListener() method removes an event listener.
  • const keyword defines a constant in JavaScript.
  • load lifecycle event triggers when the page finishes loading.
  • event.stopPropagation() stops the propagation of an event.
  • In localStorage, values are stored as strings.
  • The default value of this inside a class method (unbound) is undefined.
  • The syntax element.dataset.id accesses a data attribute named data-id.
  • JSON.parse() method parses a JSON string into an object.
  • Event delegation involves binding an event to a parent and using event.target.
  • If two elements have the same id, only the first one is accessible via getElementById().
  • setTimeout() defers execution.
  • The history object gives access to browser history.
  • document.getElementById() returns an Element.
  • let keyword defines a variable with block scope.
  • innerHTML returns HTML structure inside the element.
  • Object.keys(obj) returns an array of keys.
  • export keyword exports a class/module.
  • async/await handles asynchronous code.
  • fetch() method makes an HTTP request in the browser.
  • The output of typeof NaN is number.
  • {...obj} clones an object in JavaScript.
  • window.alert() shows a popup.
  • Float is not a valid JavaScript data type.
  • includes() method checks if an array includes a value.
  • Array.isArray([]) returns True.
  • === operator checks value and type.
  • new Class() creates a new instance of a class.
  • DOMContentLoaded event indicates that the DOM is ready.
  • event.target returns the source element of the event.
  • No specific keyword defines methods inside a class, just use the method name.
  • The main benefit of using OOP in browser programming is code reuse and modularity.

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