The interview is a critical part of your life as what you say in an interview matters the most and helps you in deciding your career in the future stage. If you are worried about cracking the interview as don’t know what type of questions the interviewer will ask you, then you can blindly follow our Node JS Interview questions to understand the pattern. Our team of experts and professionals ensures to create questions and answers that are usually asked in the interview with the candidates.
Node.JS is a cross-platform JavaScript environment that implements all the JavaScript codes outside the browser that you are using. It is an open-source platform when you can write a command using the command lines tools and applications to run the scripts and create a dynamic web page based on the requirements of the clients. You can create contents that are not similar to the others using a single programming language and not different languages. Considered as one of the best platforms to develop a webpage, many organizations are focusing on onboarding this platform in their operations division.
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 a 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.
Modules are the reusable block of code whose existence does not impact other code in any way. It is not supported by Javascript. Modules are introduced in ES6. Modules are important for Maintainability, Reusability, and Namespacing of Code.
Yes, Node Js is single-threaded to perform asynchronous processing. Doing async processing on a single thread could provide more performance and scalability under typical web loads than the typical thread-based implementation.
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 that 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.
Syntax:
require(path);
Node js is written in C, C++,JavaScript.It uses Google’s open-source V8 Javascript Engine to convert Javascript code to C++.
Using Node Js you can build applications like:
but is a Cross-platform I/O abstraction library that supports asynchronous I/O based on event loops. It is written in C and released under MIT Licence.
libuv support Windows IOCP, poll(4), kqueue(2), and Solaris event ports. Initially, it was designed for Node.js but later it is also used by other software projects.
Reference: https://en.wikipedia.org/wiki/Libuv
Zlib is a Cross-platform data compression library. It was written by Jean-loup Gailly and Mark Adler. In Node js, you can Zlib for Threadpool, HTTP requests, and responses compression, and Memory Usage Tuning. To use zlib in node js, you need to install the node-zlib package. After installation below is a sample code to use Zlib.
var Buffer = require(buffer).Buffer; var zlib = require(zlib); var input = new Buffer(lorem ipsum dolor sit amet); var compressed = zlib.deflate(input); var output = zlib.inflate(compressed);
Further Reading https://nodejs.org/api/zlib.html
Normally NodeJs reads the content of a file in a non-blocking, asynchronous way. Node Js uses its fs core API to deal with files. The easiest way to read the entire content of a file in nodeJs is with fs.readFile method. Below is a sample code to read a file in NodeJs asynchronously and synchronously.
Reading a file in node asynchronously/ non-blocking
var fs = require(fs); fs.readFile(DATA, utf8, function(err, contents) { console.log(contents); }); console.log(after calling readFile);
Reading a file in node asynchronously/blocking
var fs = require(fs); var contents = fs.readFileSync(DATA, utf8); console.log(contents);
Streams are special types of objects in Node that allow us to read data from a source or write data to a destination continuously. There are 4 types of streams available in Node Js, they are
In Node Js all core modules, as well as most of the community-published modules, follow a pattern where the first argument to any callback handler is an error object. this object is optional, if there is no error then in that case null or undefined is passed to the callback.
Example of the callback function
function callback(err, results) { // usually well check for the error before handling results if(err) { // handle error somehow and return } // no error, perform standard callback handling }
JIT stands for Just-in-time. A JIT compiler is a program that is used to send bytecode (it consists of instruction that can be interpreted) to the processor by converting it into instruction. After you have done writing a program, the compiler compiles the source language statements into bytecode instead of compiling them into the code that carries the information which is similar to the specific hardware platforms processor.
Relation of JIT with Node: Virtual machine of Nodejs has JIT compilation which improves the execution speed of the code. The virtual machine takes the source code and converts it to machine code in runtime. By this, the hot functions which are called very often are compiled to machine code and, hence increasing speed.
By writing the following line of code, you can create a server in Node Js.
var http =require(http); http.createServer(function(req,res){ res.writeHead(200,{Content-Type:text/plain}); res.end(Hello World\n); }).listen(1320,127.0.0.3);
A Closure is a function defined within another scope that has access to all the variables within the outer scope.
Global variables can be made local (private) with closures.
Aggregations are a set of functions that are used to manipulate the data that has been returned from a MongoDB query. In Mongoose, aggregations work as a pipeline. The aggregate function accepts the array of data transformations that are applied by data using different methods in terms of arguments.
Syntax: db.customers.aggregate([ ... aggregation steps go here ...]);
In above, aggregation is applied to data of customers.
The main difference between the put and the patch is
Put | Patch |
---|---|
The embedded entity is believed to be the modified version of the resources that are deposited on the original server. It is requested to the client to replace the stored is substituted. | In this, the information regarding the way of modifying the original server which has the resources to produce a new version is found. |
At the time of updating the resource, you need to forward the full payload as request. | At the time of updating the resource, you only need to send the parameter of the resource which you want to update. |
HTTP defines a set of request methods to perform the desired actions. These request methods are:
The revealing module pattern is similar to the Module Pattern.IT ExposES only the properties and methods you want via a returned Object.
var greeting = Hello world function greet() { console.log(greeting) } module.exports = { greet: greet }
following is the syntax of one of the methods to read from a file:
fs.read(fd, buffer, offset, length, position, callback)
This method will use a file descriptor to read the file, if you want to read a file using the file name directly then you should use another method available.
Here is the description of the parameters used -
Following is the syntax of one of the methods to write into a file:
fs.writeFile(filename, data[, options], callback)
This method will overwrite the file if the file already exists. If you want to write into an existing file then you should use another method available.
Here is the description of the parameters used:
When a theme is activated it’s what’s controlling your site, while an installed theme is simply part of your theme library and available to activate.
Following is the syntax of one of the methods to close an opened file:
fs.close(fd, callback)
Here is the description of the parameters used:
Following is the syntax of the method to get the information about a file:
fs.stat(path, callback)
Here is the description of the parameters used:
Following is the syntax of the method to truncate an opened file -
fs.ftruncate(fd, len, callback)
Here is the description of the parameters used:
Following is the syntax of the method to delete a file -
fs.unlink(path, callback)
Here is the description of the parameters used:
Following is the syntax of the method to create a directory:
fs.mkdir(path[, mode], callback)
Here is the description of the parameters used:
Following is the syntax of the method to remove a directory:
fs.rmdir(path, callback)
Here is the description of the parameters used:
Following is the syntax of the method to read a directory:
fs.readdir(path, callback)
Here is the description of the parameters used:
The __filename represents the filename of the code being executed. This is the resolved absolute path of this code file. For the main program, this is not necessarily the same filename used in the command line. The value inside a module is the path to that module file.
As the market of technology is growing every day, the career opportunities and scopes in this specific field are also increasing day by day. With the platform to write commands in a single programming language, it has become easier for companies to hire developers who have the basic knowledge and expertise of commanding and programming language. If you have the right skills to apply for this job, then you have a chance to earn more than a lakh per month based on your performance in the job. For a fresher, he or she is more likely to earn about 90,000 to 100,000 dollars per annum, while for an experienced candidate, the salary increases up to 180,000 to 200,000 dollars based on his or her skill set.
Node JS is gaining a lot of attention in the market because of its demands across all the industries that work in the technological sector. If you want to crack the Node JS interview questions, just understand and learn the answers that our experts have provided.