What does a Promise represent in JavaScript?

  • A synchronous operation
  • An asynchronous operation
  • A specific data type
  • A built-in JavaScript function
A Promise in JavaScript represents an asynchronous operation that may or may not be completed at a certain point in time. It's used to handle tasks like fetching data from a server or reading a file, which can take some time to complete. Promises provide a way to work with asynchronous code in a more structured and readable manner.

Which method should be used to handle exceptions in an async/await function?

  • try...catch
  • if...else
  • switch...case
  • throw...catch
To handle exceptions in an async/await function, you should use the 'try...catch' statement. This allows you to wrap the awaited code in a 'try' block and catch any exceptions that may occur within the 'catch' block. Using 'try...catch' ensures that your program can gracefully handle errors and prevent them from crashing your application.

Which of the following is NOT a type of polymorphism supported by JavaScript?

  • Compile-time polymorphism
  • Runtime polymorphism
  • Ad-hoc polymorphism
  • Parametric polymorphism
JavaScript supports runtime polymorphism and ad-hoc polymorphism (also known as function overloading), allowing different behavior for functions with the same name but different parameters. Parametric polymorphism is associated with generics and is not a form of polymorphism in JavaScript.

The _________ property of the XMLHttpRequest object holds the status of the XMLHttpRequest.

  • statusText
  • response
  • status
  • readyState
The status property of the XMLHttpRequest object holds the HTTP status code of the response received from the server. It indicates whether the request was successful or encountered an error. statusText contains the status message associated with the status code. response contains the response data.

How do you declare a two-dimensional array in JavaScript?

  • let arr = [[]];
  • let arr = [][[]];
  • let arr = [[], []];
  • let arr = [[],] [[]];
In JavaScript, a two-dimensional array is declared by creating an array where each element is another array. This creates a matrix-like structure. For example, let arr = [[], []]; declares a 2x2 two-dimensional array. The other options contain syntax errors or do not create a valid two-dimensional array.

The _______ method is used to handle errors in Promises.

  • .then()
  • .catch()
  • .resolve()
  • .reject()
The correct method to handle errors in Promises is the .catch() method. When a Promise is rejected, the .catch() method is called with the reason for the rejection, allowing you to handle and manage errors in your asynchronous code effectively.

JavaScript was introduced to the world in the year _________.

  • 1995
  • 2000
  • 1998
  • 1993
JavaScript was introduced to the world in the year 1995. It was first released by Netscape as part of their Navigator 2.0 web browser. JavaScript quickly gained popularity as a client-side scripting language for web development.

What is a potential downside of using async/await syntax?

  • It makes code harder to read and understand.
  • It can't be used with Promises.
  • It always leads to callback hell.
  • It reduces code efficiency.
One potential downside of using async/await is that it can make code harder to read and understand, especially for developers who are not familiar with asynchronous programming. It may lead to nested code blocks, which can be challenging to follow. However, when used correctly, async/await can make asynchronous code more readable.

Which organization developed JavaScript?

  • Microsoft
  • Mozilla
  • Netscape
  • Oracle
JavaScript was developed by Netscape. Brendan Eich created it in 10 days in September 1995. While Netscape is best known for its role in the development of JavaScript, it didn't create other popular languages like Java.

What is the output of the arithmetic expression 7 / 0 in JavaScript?

  • 0
  • Infinity
  • NaN (Not-a-Number)
  • Error
The output of the arithmetic expression 7 / 0 in JavaScript is Infinity. In JavaScript, dividing a number by 0 results in positive or negative infinity depending on the sign of the numerator. Attempting to divide by 0 does not throw an error, but it produces infinity.