JavaScript Interview Questions and Answers Set 4

31. What are callbacks?

A callback is a function that will be executed after another function gets executed. In javascript, functions are treated as first-class citizens, they can be used as an argument of another function, can be returned by another function, and can be used as a property of an object.

32. Is JavaScript case sensitive? Give an example?

Yes, JavaScript is case sensitive. For example, a function parseInt is not same as the function Parseint.

33. What boolean operators can be used in JavaScript?

The ‘And’ Operator (&&), ‘Or’  Operator (||) and the ‘Not’ Operator (!) can be used in JavaScript.

*Operators are without the parenthesis.

34. What is the role of break and continue statements?

Break statement is used to come out of the current loop while the continue statement continues the current loop with a new recurrence.

35. How are DOM utilized in JavaScript?

DOM stands for Document Object Model and is responsible for how various objects in a document interact with each other. DOM is required for developing web pages, which includes objects like paragraph, links, etc. These objects can be operated to include actions like add or delete. DOM is also required to add extra capabilities to a web page. On top of that, the use of API gives an advantage over other existing models.

Weekend / Weekday Batch

36. Explain the unshift() method ?

This method is functional at the starting of the array, unlike the push(). It adds the desired number of elements to the top of an array.

37. What do you mean by BOM?

Browser Object Model is known as BOM. It allows users to interact with the browser. A browser’s initial object is a window. As a result, you may call all of the window’s functions directly or by referencing the window. The document, history, screen, navigator, location, and other attributes are available in the window object.

<script type=”text/javascript” src=”message.js”></script>  

38. What is DOM? What is the use of document object?

DOM stands for Document Object Model. A document object represent the html document. It can be used to access and change the content of html.

39. What is the use of window object?

The window object is automatically created by the browser that represents a window of a browser.

It is used to display the popup dialog box such as alert dialog box, confirm dialog box, input dialog box etc.

40. What is the use of history object?

The history object of browser can be used to switch to history pages such as back and forward from current page or another page. There are three methods of history object.

  1. back()
  2. forward()
  3. go(number): number may be positive for forward, negative for backward.