Express and Node JS Interview Questions

Express and Node JS Interview Questions

Node Js is one of the most popular and powerful server technologies today. It allows you built the entire website only in one programming Language i.e Javascript. Node js is free and open source server technology that uses Javascript to create complete web software. It runs on various platforms like Windows, Linux, Unix, Mac OS X, etc.

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Express and Node JS Interview Questions

Http defines a set of request methods to perform the desired actions. These request methods are:

  1. GET: The GET method asked for the representation of the specifies resource. This request used to retrieve the data.
  2. POST: The POST technique is utilized to present an element to the predetermined resource, generally causing a change in state or reactions on the server.
  3. HEAD: The HEAD method is similar to the GET method but asks for the response without the response body.
  4. PUT: This method is used to substitute all current representations with the payload.
  5. DELETE: It is used to delete the predetermined resource.
  6. CONNECT: This request is used to settle the TCP/IP tunnel to the server by the target resource
  7. OPTION: This method is used to give back the HTTP strategies to communicate with the target resource.
  8. TRACE: This method echoes the message which tells the customer how much progressions have been made by an intermediate server.
  9. PATCH: The PATCH method gives partial modifications to a resource.

CORS stands for Cross-Origin Resource Sharing. It a is a mechanism that uses additional HTTP headers to tell a browser to let a web application running at one origin (domain) have permission to access selected resources from a server at a different origin.

Use below code to enable CORS on NodeJS

app.use(function(req, res, next) {
  res.header("Access-Control-Allow-Origin", "*");
  res.header("Access-Control-Allow-Headers", "Origin, X-Requested-With, Content-Type, Accept");
An event is an action or occurrence recognized by software/app that is handled by event handler by writing a code that will be executed when the event fired.
Mouse move, Click, file copied or deleted are some examples of events.
In Node Js there are two types of events.
1)System Events: The event that comes from the C++ side.
2)Custom Events: Custom events are user-defined events.
require() is used to include modules from external files in Node Js. It is the easiest way to include a module in Node. Basically require is a function that takes a string parameter which contains the location of the file that you want to include. It reads the entire javascript file, executes the file, and then proceeds to return the exports object.
  • readFile load the whole file which you had marked to read whereas createReadStream reads the complete file in the parts of the size you have declared.
  • The client will receive the data faster in the case of createReadStream in contrast with readFile.
  • In readFile, a file will first completely read by memory and then transfers to a client but in later option, a file will be read by memory in a part which is sent to clients and the process continue until all the parts finish.
Node Js is written by Ryan Dahl.

Run below command on the terminal to set default node version along multiple installed versions of node. You can list all install versions of the node by running nvm ls

nvm alias default v7.3.0
Node js is written in C, C++,JavaScript.It uses Google’s open source V8 Javascript Engine to convert Javascript code to C++.
A Javascript Engine is a program that converts code written in Javascript to something that computer processor understands.

CommonJS Modules is the Standard how to code modules are structured. It specifies an ecosystem for JavaScript outside on the server or for native desktop applications.