Which of the following is NOT a usage of JavaScript?

  • Data Analysis
  • Fetching & Displaying Data
  • Form Validation
  • Web Animations
JavaScript is primarily a web-based language used for front-end development to make web pages interactive. Tasks like Web Animations, Form Validation, and Fetching & Displaying Data are core uses. Data Analysis is typically done using languages like Python.

How can developers handle errors in callbacks to ensure a smooth user experience and debugging?

  • Ignore errors to maintain user experience.
  • Use global error handlers to catch all errors.
  • Log errors and handle them gracefully with try-catch blocks.
  • Rely on automatic error handling by JavaScript.
To ensure a smooth user experience and effective debugging, developers should log errors and handle them gracefully using try-catch blocks in the callback functions. Ignoring errors can lead to unexpected issues for users, and relying solely on global error handlers may not provide context-specific error handling. Handling errors within the callback allows developers to respond appropriately to different situations.

If a variable is declared inside a block using the let keyword, it is not accessible _________ that block.

  • Outside
  • After
  • Before
  • Within
If a variable is declared inside a block using the let keyword, it is not accessible outside that block. This is known as block scope, and it helps prevent unintended variable hoisting and leakage. Variables declared with let are limited to the block in which they are defined.

Arrow functions are not suitable for defining _________ functions.

  • async
  • generator
  • anonymous
  • recursive
Arrow functions do not work well for defining generator functions. Generator functions use the function* syntax and rely on the yield keyword, which doesn't behave as expected in arrow functions. Therefore, the correct option is generator.

The mechanism of closing over variables is a core concept in ________ programming in JavaScript.

  • Functional
  • Object-Oriented
  • Asynchronous
  • Procedural
The mechanism of closing over variables is a core concept in "Functional" programming in JavaScript. Functional programming promotes the use of pure functions and emphasizes the importance of avoiding mutable state. Closures play a vital role in functional programming by allowing functions to capture and remember the surrounding state.

To iterate over the entries of an object (key-value pairs), the object should be converted to an array of arrays using Object._______.

  • entries
  • toArray
  • keys
  • values
To iterate over the entries (key-value pairs) of an object, the object should be converted to an array of arrays using Object.entries. This method returns an array containing arrays, each with two elements: the key and its corresponding value from the object. You can then iterate over these pairs.

Can arrow functions be used as constructors?

  • No
  • Yes
  • Only in ES6
  • Only in ES5
No, arrow functions cannot be used as constructors in JavaScript. Unlike regular functions, arrow functions do not have their own 'this' binding, and they cannot be used with the 'new' keyword to create instances of objects. Arrow functions are primarily used for creating concise function expressions.

You are debugging a piece of code and encounter a variable declaration let [a, b, ...rest] = [10, 20, 30, 40, 50];. What will be the value of rest?

  • [30, 40, 50]
  • [10, 20]
  • [20, 30, 40, 50]
  • [undefined, undefined]
The value of rest will be [30, 40, 50]. This code uses destructuring assignment to assign the first two elements to a and b, and the rest of the elements to rest using the rest parameter (...). So, a will be 10, b will be 20, and rest will contain [30, 40, 50].

When you want to store multiple values in a single variable, you should use a(n) _________.

  • "array"
  • "object"
  • "string"
  • "function"
To store multiple values in a single variable in JavaScript, you should use an array. An array is a data structure that can hold multiple values of different data types. It is created using square brackets, like this: var myArray = [value1, value2, value3];. Arrays are versatile and commonly used for tasks like storing lists of items or organizing data.

Which property allows you to change the HTML content of an element?

  • textContent
  • innerText
  • innerHTML
  • innerTextContent
The innerHTML property allows you to change the HTML content of an element in JavaScript. It is often used to set or modify the content of an element and can include HTML tags. However, be cautious when using innerHTML to avoid potential security issues, such as cross-site scripting (XSS).