Node JS Interview Questions for experienced – 5 yrs

1. What is RedirectPermanent in ASP.Net?

The RedirectPermanent method overload provides a 301 HTTP status code in the response and includes the URL to redirect the request to. A 301 HTTP status code is a standard code in an HTTP response. It indicates that a permanent redirection exists, and it provides that the redirection location.

2. Explain the working of passport authentication.

Passport authentication identifies a user by using his or her email address and a password and a single Passport account can be used with many different Websites. Passport authentication is primarily used for the public Web sites with thousands of users.

3. How do you register JavaScript for webcontrols?

If we wanted to run a JavaScript function when the user clicks a button, we added a function name to the “onclick” property in the button’s HTML code. You can also register the event handlers when you have more complex functions you want to hook to your HTML elements.

4. Differentiate strong typing and weak typing

Strong typing means that the type check is done at compile time and weak typing means that the type check is done at run time.NET languages incorporate the strong typing.

5. How can we force all the validation controls to run?

The Page.Validate() method is used to force all the validation controls to run and to perform the validation.

6. What is the appSettings Section in the web.config file?

The AppSetting section in the configuration file is a section that allows us to keep configurable and the application wide settings that an application requires in order to perform the tasks properly. This helps in easy maintenance and deployment of the application.

7. What Is The Difference Of Using Var And Not Using Var In Repl While Dealing With Variables?

If var the variable is declared within the scope you are in (e.g. of the function). If you don’t use var , the variable bubbles up through the layers of scope until it encounters a variable by the given name or the global object , where it then attaches.

8. How To Check The Already Installed Dependencies Which Are Globally Installed Using Npm?

Global Modules are generally located at the user’s home directory, though we can change the path where global modules reside.

Lists local modules within current dir: npm list.

Lists global modules:npm list –global OR npm list –g // It will list all the top level modules with its dependencies.

9. Explain the working of assert in Node.js

Assert is the most elementary way to write tests and to provide no feedback when running the test unless one fails. The assert module provides a simple set of assertion tests that can be used to test invariants. The module is intended for internal use by Node.

10. What is the stream in Node.js? What are its types?

A stream is a way of data-handling that helps to obtain a sequential output by reading or writing the input (files, network communications, and any kind of end-to-end information exchange).The four types of streams are

readable,
writable,
duplex,
transform.

11. List and explain the timing features of Node.js.

The timer module in Node.js consists of functions that help to control the timings of code execution.
The callback parameter holds the function that to be executed.
The delay parameter holds the number of milliseconds to wait before calling the callback function.
The args parameter holds the optional parameter.

12. Explain readFile and createReadStream in Node.js.

readFile will read the file completely into memory before making it available to the User. createReadStreamwill read the file in chunks of the size which is specified beforehand.

13. Does Node.js provide a Debugger?

CLI Debugger supported by the Node. js Foundation which uses the Inspector Protocol. A version is bundled with Node. js and can be used with node inspect myscript.js. The latest version can also be installed independently (e.g. npm install -g node-inspect ) and used with node-inspect myscript.js.

14. Explain the concept of JIT and highlight its relation with Node.js.

JIT stands for Just-in-time which is a program which is used to send bytecode (it consists of instruction that can be interpreted) to the processor by converting it into instruction. Relation of JIT with Node is Virtual machine of Node.js has JIT compilation which improves the execution speed of the code.

15. What is the difference between fork () and spawn () methods in Node.js?

Spawn is useful when want to make a continuous data transfer in binary/encoding format — e.g. transferring a 1 Gigabyte video, image, or log file. Fork is useful when want to send individual messages — e.g. JSON or XML data messages.

16. State the steps to write an Express JS application.

First create a directory for the new application and navigate into it.
Use the npminit command to create a package.json file for the application.
Now install Express in the myapp directory and save it in the dependencies list of your package.json file. npm install express.

17. Which is the first argument typically passed to a Node.js callback handler?

The first parameter of the callback is the error value. If the function hits an error, then they typically call the callback with the first parameter being an Error object. If it cleanly exits, then they will call the callback with the first parameter being null and the rest being the return value(s).

18. What are the functionalities of NPM in Node.js?

Node Package Manager provides two main functionalities:

It provides online repositories for node.js packages/modules which are searchable on search.nodejs.org. It also provides command line utility to install Node.js packages, do version management and dependency management of Node. js packages.

19. What are “streams” in Node.js? Explain the different types of streams present in Node.js.

Streams are one of the fundamental concepts of Node.js and are a type of data-handling methods, used to read or write input into output sequentially. Streams are used to handle reading/writing files or exchanging information in an efficient way.

There are four fundamental stream types in Node. js:

Readable. Writable. Duplex. Transform streams.

20. What is “callback hell” and how can it be avoided?

Callback Hellis an anti-pattern seen in code of asynchronous programming. It is a slang term used to describe and unwieldy number of nested “if” statements or functions. If you are not expecting your application logic to get too complex, a few callbacks seem harmless.

21. How does Node.js handle child threads?

Node.js is a single-threaded language which uses the multiple threads in the background for certain tasks as I/O calls but it does not expose child threads to the developer.

22. For what require() is used in Node Js?

Require() is a built-in function to include external modules that exist in separate files. It reads a JavaScript file, executes it, and then proceeds to return the export object.

23. Explain module.exports in Node Js ?

Exports is the object that is returned as the result of a required call. The exports variable is initially set to that same object (i.e, it’s a shorthand “alias”), so in the module code you would usually write something like this:

myFunc1 = function(); let myFunc2 = function();

24. Differentiate between readFile vs createReadStream in Node.js?

readfile loads the whole file into the memory you pointed out, the fs. createReadStreamreads the entire file in chunks of sizes that you specified. The client will also receive the data faster with fs. createReadStream since it is sent in chunks while it’s being read.

25. List down the various timing features of Node.js.

Callback parameter holds the function that to be executed.
Delayparameter holds the number of milliseconds to wait before calling the callback function.
Argsparameter holds the optional parameter.

26. Explain the concept of Punycode in Node.js?

Punycode is an encoding syntax which is used to convert Unicode (UTF-8) string of characters to basic ASCII string of characters. Since host names only understand ASCII characters so Punycode is used. It is used as an internationalized domain name (IDN or IDNA).

27. Is cryptography supported in Node.js?

The Node JS Crypto module supports cryptography and provides cryptographic functionality that includes a set of wrappers for open SSL’s hash HMAC, cipher, decipher, sign and verify functions.

28. How do you handle large file uploads in Node.js?

To handle large file uploads in Node.js, you can use streams to process the data incrementally rather than loading the entire file into memory. Libraries like multer or busboy can help manage multipart file uploads.

29. What is the http.Agent class in Node.js?

The http.Agent class in Node.js manages connections when making HTTP requests. It pools and reuses sockets for HTTP requests, optimizing performance by keeping connections alive rather than opening a new one for each request.

30. How does Promise.all() work in Node.js?

Promise.all() takes an array of promises and resolves once all promises are fulfilled or rejects as soon as one promise is rejected. It is useful for executing multiple asynchronous operations in parallel and waiting for all of them to complete.

31. What are the types of timers available in Node.js?

Node.js provides setTimeout(), setInterval(), and setImmediate() for managing timers. setTimeout() schedules a function after a specified delay, setInterval() repeatedly calls a function at specified intervals, and setImmediate() executes a function in the next iteration of the event loop.

32. Explain the difference between fork() and spawn() in Node.js.

Both fork() and spawn() are used to create child processes. fork() is specifically used to create a new Node.js process that can communicate with the parent process via IPC (Inter-Process Communication), whereas spawn() creates a new process and is used for running external commands.

33. What is the async_hooks module in Node.js?

The async_hooks module provides an API to track asynchronous resources created inside a Node.js application. It is useful for diagnosing and debugging asynchronous operations.

34. What is the difference between exports and module.exports?

exports is a reference to module.exports. You can add properties to exports like exports.someFunction = …, but if you reassign exports (exports = someFunction), it will not update module.exports. module.exports is the actual object returned when a module is required.

35. What is the purpose of the package-lock.json file?

The package-lock.json file is generated automatically with npm install. It locks the exact versions of all installed packages and their dependencies, ensuring consistency across different environments.

36. How does the require() function work in Node.js?

The require() function is used to load modules in Node.js. It caches modules after the first load to improve performance. When require() is called, Node.js resolves the module path, loads and executes the module, and returns the module.exports object.

37. How do you secure a Node.js application?

Securing a Node.js application involves steps such as validating user input, using HTTPS, avoiding vulnerable dependencies (using tools like npm audit), implementing proper authentication/authorization, using secure cookie handling, and preventing CSRF, XSS, and SQL injection attacks.

38. What is the purpose of the package-lock.json file?

39. What are some methods for handling memory leaks in Node.js?

To handle memory leaks in Node.js, developers can use profiling tools like Chrome DevTools or Node’s built-in –inspect flag to find memory allocation issues. Other methods include using weak references, ensuring event listeners are removed properly, and avoiding global variables.

40. What is libuv in Node.js?

libuv is a multi-platform support library that Node.js uses to handle asynchronous I/O operations. It abstracts the underlying system’s functionality (file system, network, etc.) to provide non-blocking event-driven behavior.

41. How do you improve the performance of a Node.js application?

Performance improvements in Node.js can include using clustering, caching, employing efficient database queries, using streams instead of loading large files into memory, and optimizing code execution with asynchronous patterns like async/await.

42. What is the difference between Buffer and Stream in Node.js?

Buffer is a class in Node.js used to store raw binary data. It is primarily used when dealing with binary data like files or TCP streams. Stream, on the other hand, represents a sequence of data chunks and is more efficient for handling large amounts of data.

43. How do you manage error handling in asynchronous code in Node.js?

Error handling in asynchronous code is typically done using callback functions that accept an error as the first argument (error-first callbacks). In modern Node.js, async/await is preferred for better readability, with try…catch blocks used to catch errors.

44. What is the difference between process.nextTick() and setImmediate()?

process.nextTick() defers the execution of a callback until the next iteration of the event loop, while setImmediate() schedules a callback to be executed in the next iteration, after I/O events. process.nextTick() runs before setImmediate().

45. How does Node.js handle asynchronous I/O operations?

Node.js handles asynchronous I/O using non-blocking APIs. Instead of waiting for I/O operations to complete, it registers a callback function and continues executing the rest of the code. Once the I/O operation completes, the callback is executed.

46. Create a simple file upload server using Node.js.

47. Implement a rate-limiting middleware in Node.js.

48. Implement a function that returns a promise-based delay using setTimeout().

function delay(ms) { return new Promise((resolve) => { setTimeout(resolve, ms); }); } delay(2000).then(() => { console.log(‘Executed after 2 seconds’); });

49. What is Event-Driven Programming in Node.js?

Event-Driven Programming is a paradigm in Node.js where the flow of the program is determined by events like user actions, network requests, or messages from other programs. In Node.js, this is managed by an event loop that listens for events and triggers corresponding callback functions. Node.js provides the EventEmitter class to handle events and their associated listeners.

50.What is the difference between process.nextTick() and setImmediate() in Node.js?

Both process.nextTick() and setImmediate() are used to schedule callbacks, but they have different execution timing.

process.nextTick(): It adds the callback to the next iteration of the event loop, meaning it is processed before any I/O tasks and timers in the event loop.

setImmediate(): It schedules the callback to be executed on the next iteration of the event loop after I/O events are processed.

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Node JS Interview Questions for experienced – 5 yrs