javascript developer job interview questions.


Randstad Technologies has over 35 years of experience recruiting for the IT sector, matching the right candidate with the best IT role. Part of the job hunting process calls on the candidate to perform well at the interview stage.

In order to help candidates throughout the preparation process, we gathered 50 commonly asked interview questions for JavaScript developer job candidates:

Technical JavaScript interview questions.

  • Define global variables and describe how they are declared.
  • What problems may arise with the use of globals?
  • Describe how you would organise your JavaScript code.
  • What differences are there between undefined and null? 
  • In terms of JavaScript, to what does ‘this keyword’ refer?
  • What are your views on JavaScript frameworks?
  • How would you gracefully handle an error in JavaScript?
  • Are you able to explain how inheritance works in JavaScript?
  • Can you describe how JavaScript timers work?
  • Describe one drawback of using them.
  • Can you describe event bubbling?
  • Describe the difference between an Interface and an Abstract class.
  • Why and when is a garbage collection in Java used? 
  • In respect to multithreading, what is synchronisation?
  • Explain pass by reference and pass by value.
  • Describe HashMap and Map.
  • Describe the difference between Swing and AWT.
  • Describe the difference between a constructor and a method.
  • What is the significance of public, private, protected and default modifiers both singly and in combination and what is the effect of package relationships on declared items qualified by these modifiers.
  • For method declarations, what is the catch or declare rule? What, in your opinion, is the simplest way to find out the time a metold takes for execution without using a profiling tool?
  • Describe static in Java.
  • How, using one line of code, can one prove that the array is not null but empty?
  • Explain the different types of inner classes.
  • Describe the difference between declaring a variable and defining a variable. 
  • Is a top-level class able to be private or protected?
  • What should one take care of during the serialisation of the object to a file?
  • What is the purpose of wrapper classes?
  • Describe the two different ways of handling exceptions. 
  • What is the initial state of a thread when it has been created and started?
  • Describe the difference between Assignment and Initialisation. 
  • What are the modifiers that may be used top-level class? 
  • Describe interface and its purpose.
  • Describe the life cycle of a servlet. 
  • Describe cookies and their use. 
  • Describe method overloading.
  • How, using its Iterator, do you traverse through a collection? 
  • What advantages does ArrayList have over arrays?
  • How do you obtain an Array from an Arraylist?
  • Describe a KeySet View. 
  • Describe a Value Collection View. 
  • Describe an EntrySet View. 
  • State and describe the different forms of Polymorphism. 
  • Is it possible to instantiate an interface? 
  • Is it possible to create an object for an interface?
  • Describe Abstraction.
  • Describe Encapsulation.
  • is the method that must be implemented by all threads?
  • What is the difference between synchronized methods and synchronized statements?
  • Define Externalizable. 
  • What alternatives are there to inheritance? 

Personal JavaScript interview questions.

  • In our industry, what are some important trends that you see?
  • What do you feel is an appropriate salary for this position?                                        
  • What are your reasons for leaving your previous/present job?        
  • Describe yourself professionally in a few words.
  • How do you remain abreast of new developments in technology? 
  • If your previous manager was in the room with us, what do you think he would have to say about you?
  • What is your favourite aspect of being a java developer?
  • How capable do you think you are at handling stress? 

Scenario interview questions.

  • What is your troubleshooting process?
  • Would you describe yourself as a problem solver? If so, why? Can you give any example

The company interview questions.

  • What do you know about our company and our products?   
  • Why do you want to work for this organisation?     

Career-based JavaScript interview questions.

  • What are some things that you look for in a job?  
  • What long-term goals do you have and why?
  •  In two or three years from now, what do you see yourself doing? 
  • Describe two or three of your accomplishments over the past few years that you are most proud of.