10+ Fullstack Javascript Developer Interview Questions and Answers

Print numbers 1 to n with a delay of i seconds for each number.

• Use a loop to iterate from 1 to n

• Use setTimeout function to delay the printing of each number

• Use let instead of var to avoid closure issues

• Promisify the solution by returning a promise

let, var and const are all used to declare variables in JavaScript, but they differ in their scope and mutability.

• let has block scope and can be reassigned

• var has function scope and can be reassigned

• const has block scope and cannot be reassigned, but its properties can be mutated

To find the intersection node of two linked lists, iterate through both lists and compare each node until a common node is found.

• Iterate through both linked lists simultaneously

• Compare each node of the lists until a common node is found

• If the lists have different lengths, align the starting points by advancing the longer list

Design a database schema for nested comments on a post

• Create a table for posts with a unique ID

• Create a table for comments with a unique ID, post ID, and parent comment ID

• Use foreign keys to link comments to posts and parent comments

• Use a recursive function to retrieve nested comments

Maps, reduce, hoisting, strings, var, let, const are important concepts in JavaScript development.

• Maps: Used to transform elements in an array without changing the original array.

• Reduce: Used to reduce an array to a single value by applying a function to each element.

• Hoisting: Refers to the behavior in JavaScript where variable and function declarations are moved to the top of their containing scope.

• Strings: Data type used to represent text in JavaScript.

• Var: Declares a varia...read more

Higher order functions are functions that take other functions as arguments or return functions as their output.

• Higher order functions can be used to create more flexible and reusable code.

• They allow for functions to be composed and combined in various ways.

• Examples of higher order functions include map, filter, and reduce in JavaScript.

• Higher order functions can also be used for currying and partial application.

Event loops are mechanisms in programming languages that allow for asynchronous execution of code.

• Event loops handle the execution of multiple tasks in a non-blocking manner.

• They continuously check for tasks in the event queue and execute them one by one.

• Event loops are commonly used in JavaScript to handle asynchronous operations like setTimeout, setInterval, and AJAX requests.

Custom hook is a reusable function in React that allows you to extract component logic into a separate function.

• Create a function starting with 'use' keyword (e.g. useCustomHook)

• Use useState, useEffect, useContext, or other hooks inside the custom hook

• Return the necessary values or functions from the custom hook

Remove the nth node from a linked list

• Traverse the linked list to find the nth node

• Update the pointers to skip over the nth node

• Handle edge cases like removing the head node

Middleware in Node.js is a function that has access to the request and response objects, and can modify or terminate the request-response cycle.

• Middleware functions are executed sequentially in the order they are defined.

• They can be used for tasks such as logging, authentication, error handling, etc.

• Example: Express.js uses middleware extensively for handling requests.