Javascript Interview Questions and Answers

Frequently Asked JavaScript Interview Questions

Q1. What are the data types supported by JavaScript?

Ans: JavaScript supports undefined, null, boolean, string, symbol, number and object data types.

Q2. List some of the features of JavaScript

Ans: Some of the salient features of JavaScript are as follows:

• Lightweight, interpreted programming language
• Designed for creating network-centric applications
• Complementary to and integrated with Java
• An open,  cross-platform scripting language

Q3. Is JavaScript case-sensitive?

Ans: Yes, JavaScript is a case sensitive language and requires the language keywords, variables, function names, and any other identifiers to be always typed with a consistent capitalization of letters.

Q4. What are the advantages of JavaScript?

Ans: The advantages of JavaScript are as follows:

• Less server interaction because user input can be validated before sending the page off to the server. It saves server traffic and results in a lesser load on the server.
•  Immediate feedback to the visitors, so they need not wait for a page to reload before verifying their input.
• Increased interactivity by means of interface creation that react when the user rolls the mouse over them or activates them via the keyboard.
• Richer interfaces can be created using JavaScript such as drag-and-drop components and sliders for great user experience.

Q5. How can you create an object in JavaScript?

Ans: Following is a code for object creation:

       var emp = {

name: "Daniel",

age: 23

};

Q6. What would be the result of 2+5+”3″?

Ans: 2 and 5 are integers, so they will be added numerically. 3 is a string and therefore it will be concatenated resulting in 73 as the answer. The ” ” represents 3 as a string rather than a number.

Q7. What is the difference between Call & Apply?

Ans: The call() method calls a function with the given value and individually provided arguments as follows:

       fun.call(thisArg[, arg1[, arg2[, ...]]])

The apply() method calls a function with the given value and arguments provided as an array as follows:

       fun.apply(thisArg, [argsArray])

Applications of MeritTrac Assessment Solutions

MeritTrac’s range of technology-driven assessments has been developed to make assessments convenient, quick, reliable and accurate. In addition to being useful during recruitment drives, our assessment solutions also come in handy for workforce development. 

Our JavaScript coding assessments will help recruiters and hiring managers to select highly skilled JavaScript programmers and developers. The results of the assessments will serve as the basis to decide on the candidates who will be called for a face-to-face interview. Therefore, recruiters and hiring managers can focus their time and attention on the relevant candidates rather than spending their time interviewing every candidate. The interviewers can have a list of core Java interview questions for ready reference. It will help them easily and satisfactorily judge the suitability of the candidates for the job position.

MeritTrac has assessment solutions specifically designed to gauge the strengths and weaknesses of the existing JavaScript workforce of the organisation. The performance results will give the L&D team an idea to come up with a specific training program to address the shortcomings and equip the workforce with the necessary skills.

Criteria for Code Evaluation

Following are some of the criteria on which a candidate’s source code may be evaluated:

• Effective class, method, and variable names that convey the purpose and meaning of the named entity 
• Effective top-down decomposition of algorithms with:
  • no code duplication
  • Factoring out common codes into separate routines
  • Highly cohesive routines with each routine performing a single task or a small number of highly related tasks
  • Routines performing multiple tasks should call different subroutines to perform each subtask
  • Routines should be relatively short in most cases with many routines less than 20 lines, almost all routines less than 50 lines and very rarely routines longer than 100 lines.
• Code layout should be readable and consistent with features such as placement of curly braces, code indentation, wrapping of long lines and layout of parameter lists in place
• Effective source tree directory structure with proper organization into subdirectories
• Effective file organization with each class placed in a separate file or two separate files of .h and .cpp 
• Correct exception handling as described in the specification
• Good unit test cases as per the requirements mentioned in the project specification

Candidates who clear the coding assessment will then face the interview panel. The interviewers can have a ready list of JS interview questions to quickly and objectively get over the interview meeting as well.