Top 10 JavaScript Interview Questions And Answers 

JavaScript Interview questions

Programming interview knocking on your door? This may sound scary and stress you out. However, if you prepare decently, your confidence will overcome the stress. To practice for your upcoming programming interview, there are dozens of topics that you should master. JavaScript interview questions fall under the essential category of programming topics you should master. 

Top 10 JavaScript Interview Questions 

  1. What Is JavaScript?

JavaScript is an object-oriented lightweight scripting language used for client-side and server-side validation. JavaScript code can be inserted into HTML pages and be interpreted by web browsers. 

  1. What Are JavaScript Data Types?

JavaScript supports 7 data types. These are:

  • Null – presents intentionally absent object values such as nothing or empty,
  • Number – shows integer and fractional number values,
  • String – presents a row of one or more characters combined with numbers, letters, and other symbols, 
  • Symbol – presents identifiers for each object in the code ,
  • Boolean – assigns the true or false value,
  • Object – used for storing data collections, 
  • Unknown – shows non-assigned values, 
  1. What Are Some Key Features of JavaScript?
  • JavaScript is an open-source cross-platform
  • It is lightweight 
  • It is object-oriented 
  • Complementary to HTML, Java, and other technologies
  • It is a network-centric platform 
  1. What Are The Differences Between JavaScript And Java?
Object-oriented programming scriptObject-oriented programming language
JavaScript code is written in text and only needs interpretation.Java code should be compiled. Hence, it is more complicated. 
JavaScript needs to be integrated into HTML for further interpretation and execution. Java is a standalone programming language. 
A web browser is required to run JavaScript programs.No web browser is required to run Java.
  1. What Are The Advantages of JavaScript?

Widely used. JavaScript is widely used nowadays as it is easy to interpret. Due to this, many popular companies such as Amazon and Google use JavaScript for running their online platforms. 

Lightweight. We introduced the light weight as one of the key features of JavaScript. However, we should also note that this stands out as a big advantage as online platforms strongly prefer using lightweight programming languages and scripts to maximize the speed and the space.

Flexibility. As mentioned earlier, JavaScript complements HTML, Java, and other programming languages. Due to this factor, this scripting language is more convenient since it can operate alongside other programming languages or be embedded into different webpages. 

Rich interfaces. JavaScript is a user-friendly scripting language as it enables to activate functions like using drag-and-drop items and including sliders to make the user experience smoother by providing a richer interface functionality. 

Multifuntionality. JavaScript is used both for front-end and back-end development. For the back-end development the system uses NodeJS. For front-end development, JavaScript has many libraries like ReactJS, AngularJS, VueJS, etc. 

Check out these free ReactJS, AngularJS, and VueJS courses available on WildLearner online learning platform. 

  1. How To Embed A JavaScript Element Into HTML?

There are 4 ways in which you can embed a JavaScript Element into HTML. 

  • Inline, between a pair of <script> and </script> tags


  • From an external file specified by the src attribute of a <script> tag
  • In an HTML event handler attribute, such as onclick or onmouseover
  • In a URL that uses the special JavaScript: protocol.
  1. What Is Callback in JavaScript?

The callback function runs after another JavaScript function has finished. Hence, it is defined as a function passed as an argument to another function. 

  1. What Are Some JavaScript Built-In Methods?

link() – returns string embedded in an <a> tag

exec() – tests the match in the string 

match() – used for matching a regular expression against a string

reduce() – reduces the array to a single value 

round() – returns the value of a number rounded to the nearest integer 

pop() – removes and returns the last element from an array 

  1. How To Create A Cookie on JavaScript?

To create a cookie on JavaScript, you would simply need to assign a string value to the document.cookie object.  Your operation written in the code should look like this:



  1. What Is a Typed Language?

There are two types of typed languages: statically typed and dynamically typed languages. 

In a dynamically typed language, the type checks occur when the program is executing. Furthermore, in this language, the variable can hold multiple types. 

In a statically typed language, the type check happens before the program starts running. 

How To Prepare For A JavaScript Interview?

Whether you are a complete beginner who is new to programming or an expert who wants to warm up a little bit to feel more relaxed when answering JavaScript interview questions, WildLearner has your back! 

WildLearner is a free online learning platform that offers dozens of programming courses in various areas of programming. Starting from JavaScript as the most widely used and well-known programming scripting language and continuing to the more challenging Android Development categories such as Java, WildLearner offers free access to all these courses. 

How To Start Using WildLearner?

Using WildLearner is easy. Simply create an account here by filling out the necessary information or signing up with an existing Facebook, Google, or Apple account. Next, start exploring the course catalog and choose whichever course you are interested in. 

After completing the free course, do not forget to download your certificate, which will prove the effort you have put in and the knowledge and skills you have gained.