300+ Junior Software Developer Interview Questions and Answers

JavaScript basics, React concepts, array manipulation

• let, var, and const are used to declare variables in JavaScript with different scoping rules

• Single page application is a web application that dynamically updates the content without reloading the page

• Virtual DOM is a lightweight copy of the actual DOM used by React to improve performance

• To separate even and odd values in an array, use filter() method with a condition

• To remove duplicates in an array, use Set() or filter() me...read more

Given a number n, find the number just greater than n using same digits as that of n

• Convert the number to a string and sort the digits in ascending order

• Starting from the rightmost digit, find the first digit that is smaller than the digit to its right

• Swap this digit with the smallest digit to its right that is greater than it

• Sort the digits to the right of the swapped digit in ascending order

• Concatenate the digits to get the next greater number

Program to form a string with first character of all words in a given string.

• Split the string into an array of words

• Iterate through the array and extract the first character of each word

• Join the extracted characters to form the final string

Software engineering offers numerous advantages in terms of efficiency, scalability, and maintainability.

• Efficiency: Software engineering practices help in optimizing code and improving performance.

• Scalability: Proper software engineering enables the development of scalable systems that can handle increasing workloads.

• Maintainability: Well-structured software is easier to maintain, debug, and enhance over time.

• Reusability: Software engineering promotes the reuse of code compo...read more

To stop async code based on specification condition, use cancellation tokens.

• Use CancellationTokenSource to create a cancellation token

• Pass the cancellation token to the async method

• Check the cancellation token in the async method using ThrowIfCancellationRequested()

• Cancel the token when the specification condition is met

Child components are nested within parent components in React.

• Child components are rendered within parent components.

• Parent components can pass data and functions down to child components through props.

• Child components can communicate with parent components through callbacks.

A mixin is a way to add functionality to a class without using inheritance. Ruby does not support multiple inheritance due to potential conflicts.

• Mixins in Ruby are achieved using modules, which can be included in classes to add methods and attributes.

• Ruby does not support multiple inheritance because it can lead to the diamond problem, where conflicting methods from different parent classes cause ambiguity.

• Instead of multiple inheritance, Ruby encourages the use of mixins an...read more

Yes, I am familiar with SQL and can demonstrate how to implement the structure.

• SQL is a standard language for storing, manipulating, and retrieving data in databases.

• To implement the structure in SQL, you would use CREATE TABLE statement to define the structure of a table.

• For example, CREATE TABLE Students (id INT, name VARCHAR(50), age INT); would create a table named Students with columns id, name, and age.

It is not possible to accurately estimate the number of lines of code that can be written in one day.

• The number of lines of code that can be written in a day depends on various factors such as complexity, requirements, and experience.

• It is important to focus on writing clean and efficient code rather than just aiming for a specific number of lines.

• Collaboration and teamwork can also impact the productivity and speed of coding.

• Providing an estimate without analyzing the specif...read more

Redux is a predictable state container for JavaScript apps, commonly used with React to manage application state.

• Redux helps in managing the state of the application in a predictable way.

• It provides a single source of truth for the state of the application.

• Redux allows for easier debugging and testing of the application.

• Actions are dispatched to update the state in Redux.

• Reducers specify how the state changes in response to actions.

You can use an ArrayList in Java to dynamically change the size of the array without creating a new array.

• Use ArrayList<String> instead of String[] to store strings in a dynamic array.

• You can add or remove elements from the ArrayList as needed without creating a new array.

• Example: ArrayList<String> strings = new ArrayList<String>(); strings.add("Hello"); strings.add("World");

Different programming languages have unique syntax for printing 'Hello, World!'. Here are some examples.

• Python: print('Hello, World!')

• Java: System.out.println('Hello, World!');

• JavaScript: console.log('Hello, World!');

• C: printf('Hello, World!');

• Ruby: puts 'Hello, World!'

• PHP: echo 'Hello, World!';

Callbacks are methods that are called at certain points in an object's lifecycle. Destroy permanently deletes a record, while delete marks it as deleted.

• Validation callbacks are methods that are called before or after validations on an object. They are used to ensure data integrity.

• Destroy method permanently deletes a record from the database, including associated records. It does not trigger callbacks or validations.

• Delete method marks a record as deleted in the database, bu...read more

In Spring Boot, PUT is used to update an existing resource, while POST is used to create a new resource. Input validation can be done using annotations like @Valid.

• Use PUT method to update an existing resource

• Use POST method to create a new resource

• Validate input using annotations like @Valid in Spring Boot

Maximize loot from houses without robbing adjacent ones using dynamic programming.

• Use dynamic programming to store maximum loot at each house index.

• If robbing house i, add its value to the maximum loot from house i-2.

• If not robbing house i, carry forward the maximum loot from house i-1.

• Example: For houses [2, 7, 9, 3, 1], max loot = 2 + 9 + 1 = 12.

Use GROUP BY and HAVING clause to find duplicate rows in a table without using DISTINCT.

• Use GROUP BY to group rows with the same values together

• Use HAVING clause to filter out groups with only one row

• Select columns to display duplicate rows

Exception handling in C++ and Java

• C++ uses try-catch blocks to handle exceptions

• Java uses try-catch-finally blocks to handle exceptions

• Both languages have a hierarchy of exception classes

• C++ has the throw keyword to throw an exception

• Java has the throw keyword to throw an exception

• C++ allows for custom exception classes to be created

• Java has predefined exception classes like NullPointerException

Count the number of perfect subarrays in an array where odd values are at odd positions and even values are at even positions.

• Iterate through the array and keep track of the count of odd and even numbers encountered so far.

• If the count of odd and even numbers at the current index matches the index itself, increment the count of perfect subarrays.

• Example: For array [2, 1, 3, 4], there are 3 perfect subarrays: [2, 1], [1, 3, 4], [3, 4].

Hashing is a technique to map data to a fixed-size value. To retain unique elements in a collection, use a hash set.

• Create a hash set to store unique elements

• Iterate through the collection and add each element to the hash set

• If an element already exists in the hash set, skip adding it to retain only unique elements

API testing is the process of testing APIs to ensure they meet functionality, reliability, performance, and security requirements.

• API testing involves testing the functionality, reliability, performance, and security of APIs.

• It focuses on verifying that the API works as expected, returns correct data, and handles errors properly.

• API testing can be done manually or using automated tools like Postman or SoapUI.

• Examples of API testing include testing endpoints, data validation, ...read more

A library is a collection of functions or classes that can be called by an external program, while a framework is a set of libraries that provide a structure for building applications.

• Library is used by the developer to perform specific tasks, while a framework dictates the overall structure of the application.

• Libraries are more flexible and allow developers to pick and choose which components to use, while frameworks have a more rigid structure.

• Examples of libraries include ...read more

useEffect is used to perform side effects in functional components, while useRef is used to persist values between renders.

• useEffect is used for side effects like data fetching, DOM manipulation, etc.

• useRef is used to persist values like accessing DOM elements, maintaining mutable variables, etc.

• Example: useEffect can be used to fetch data from an API when a component mounts, useRef can be used to store a reference to an input field.

Input and output functions in C language are used to interact with the user and the external environment.

• Input functions in C include scanf() for reading input from the user and getchar() for reading a single character.

• Output functions in C include printf() for displaying output to the user and putchar() for displaying a single character.

• File input and output functions in C include fopen(), fclose(), fread(), and fwrite() for reading from and writing to files.

Java is a statically typed, object-oriented programming language, while Python is dynamically typed and focuses on simplicity and readability.

• Java is statically typed, meaning variables must be declared with a specific data type, while Python is dynamically typed.

• Java is more verbose and requires more code to accomplish tasks compared to Python.

• Python emphasizes simplicity and readability, making it easier for beginners to learn and use.

• Java is commonly used for building ente...read more

Multithreading allows multiple threads to run concurrently, while OOP is a programming paradigm based on the concept of objects.

• Multithreading allows for parallel execution of multiple threads within a single process.

• OOP is a programming paradigm that uses objects to represent data and methods to manipulate that data.

• In multithreading, each thread has its own stack and runs independently, while in OOP, objects encapsulate data and behavior.

• Example of multithreading: running a...read more

Many to many vs has and belongs to many association, and explanation of polymorphic association.

• Many to many association involves a join table to connect two models with a many-to-many relationship.

• Has and belongs to many association is a simpler version of many to many, where the join table is hidden.

• Polymorphic association allows a model to belong to more than one other model, using a single association.

• Example: Many to many - Students and Courses, HABTM - Users and Roles, ...read more

Sensitive information in a web application can be secured through encryption, access controls, secure coding practices, and regular security audits.

• Encrypt sensitive data at rest and in transit using strong encryption algorithms.

• Implement access controls to restrict unauthorized access to sensitive information.

• Follow secure coding practices to prevent common vulnerabilities like SQL injection and cross-site scripting.

• Regularly conduct security audits and vulnerability assessm...read more