Aspire Systems – Node JS Interview Questions

Here is the list of Node JS Interview Questions which are recently asked in Aspire Systems company. These questions are included for both Freshers and Experienced professionals. Our Node JS Training has Answered all the below Questions.

1. What are LTS versions of Node.js?

When a new odd version is released, the previous even version undergoes transition to Long Term Support (LTS), which gives that version 18 months of active support from the date it is designated LTS. After these 18 months expire, an LTS release receives an additional 12 months of maintenance support.

2. 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.

3. What is stub in Node.js?

Stubs can be wrapped into existing functions. When we wrap a stub into the existing function the original function is not called. Stubs are functions or programs that affect the behavior of components or modules. Stubs are dummy objects for testing. Stubs implement a pre-programmed response.

4. What is Event Loop?

The event loop is what allows Node.js to perform non-blocking I/O operations despite the fact that JavaScript is single-threaded and by offloading operations to the system kernel whenever possible. Since most modern kernels are multi-threaded, they can handle multiple operations executing in the background

5. What is 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 and transform.

6. 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.

7. Explain readFile and createReadStream in Node.js.

readFilewill 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 before hand.

8. 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.

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9. Describe the exit codes in Node.js.

Node will exit with a 0 status code when no more async operations are pending. Internal JavaScript Evaluation Failure - The JavaScript source code internal in Node's bootstrapping process failed to return a function value when evaluated.

10. Why is NODE_ENV used?

NODE_ENV specifically is used to state whether a particular environment is a production or a development environment. A common use-case is running additional debugging or logging code if running in a development environment.

11. What is Event Emitter in Node.js?

Node.js uses events module to create and handle custom events. The EventEmitter class can be used to create and handle custom events module. Default Value: false it automatically captures rejections.

12. What is Punycode?

Punycode is a special encoding syntax that is specifically used to convert Unicode characters (UTF-8) to ASCII, which is nothing but the restricted string character set.

13. 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.

14. Why is the buffer class used in Node.js?

The Buffer class in Node.js is designed to handle raw binary data. Each buffer corresponds to some raw memory allocated outside V8. Buffers act somewhat like arrays of integers, but aren't resizable and have a whole bunch of methods specifically for binary data.

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.

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Aspire Systems Node JS Interview Questions