- the call stack
- the event loop
- the poll phase
- the events queue
Explanation: From javascripttutorial: reference
- webpack
- crypto
- request
- chalk
Explanation: From flaviocopes docs: reference
- allocUnsafe
- concat
- from
- alloc
Explanation: From official docs: reference
- ftp
- events
- dgram
- http2
Explanation: From flaviocopes docs: reference
Q5. Which fs module method can be used to read the content of a file without buffering it in memory?
- read
- readFile
- createReadStream
- readFileSync
Explanation: From official docs: reference To minimize memory costs, when possible prefer streaming via fs.createReadStream().
Q6. Which of the following DNS module methods uses the underlying OS facilities and does not necessarily perform any network communication?
- lookup
- resolve
- resolve4
- reverse
Explanation: From official docs: reference
- util.types.isDate(value)
- assert.isDate(value)
- console.isDate(value)
- util.date(value)
Explanation: From official docs: reference
- no, there are no modules supporting it yet
- yes, with the https or http2 modules
- yes, through the path module
- yes, with the http module
Explanation: From official docs: reference
Q9. What is the Api that is designed to insulate Addons from changes in the underlying JavaScript engine?
- A-API
- Z-API
- N-API
- X-API
Explanation: From official docs: reference
- --dev-tools
- --inspect
- --chrome
- --debug
Explanation: From official docs: reference
- node -p "process.cpus"
- node -p "util.cpus().size"
- node -p "process.os.cpus"
- node -p "os.cpus().length"
Explanation: From coderrocketfuel docs: reference
- exit
- test
- time
Explanation: From official docs: reference
- global.cache
- module.cache
- process.cache
- require.cache
Explanation: From official docs: reference
- node index.js --trace-warnings
- node --no-warnings
- node -trace-warnings
- node index.js --no-warnings
Explanation: From official docs: reference
- new Promise(child_process.exec())
- util.promisify(child_process.exec())
- util.promisify(child_process.exec)
- new Promise(child_process.exec)
Explanation: From official docs: reference
- .break
- .history
- .editor
- .save
Explanation: From official docs: reference
require('child_process').fork('script.js');
- The forked process shares the event loop with the parent process
- A new VM instance is created and the two VM instances will be shared between the forked process and the parent process.
- The forked process will have its own VM instance.
- The forked process shares the same VM thread with the parent process.
Explanation: From official docs: reference
Q18. If EventEmitter is in scope, which of the following lines of code will have an event emitter emitting a change event?
- EventEmitter.emit('change');
- EventEmitter.new().emit('change');
- (new EventEmitter()).emit('change');
- new EventEmitter('change');
Explanation: Because the EventEmitter is already in scope. No need to create new one.
- process.uptime
- process.stdout
- process
- Buffer
Explanation: process.stdout is Buffer type.
-
__pathname -
__location -
__flder -
__filename
Q21. If the child_process module methods are in scope, what is a current way to execute the command ps -ef using a child process?
- spawn("ps -ef")
- exec("ps -ef")
- exec("ps", "-ef")
- fork("ps -ef")
Reference: From official docs: reference
- stack
- trace
- debug
Q23. When you run JavaScript in a Node.js application, which of the following elements in a Node.js stack actually executes that JavaScript?
- the libuv library
- the c-ares library
- the VM (like VS or Chakra)
- the repl module
const http = require('http');
const hostname = '127.0.0.1'; const port = 3000;
const server = http.createServer((req, res) => {
res.statusCode = 200; res.setHeader("Content-Type", "text/plain"); res.end("Hello World\n");
});
server.listen(port, hostname, () => { console.log(`server running at http://${hostname}:${port}/`); });
- server running at http://localhost:3000/
- server running at port 3000
- server running at http://localhost:4000/
- server running at http://127.0.0.1:3000/
Explanation: From official docs: reference
- to provide utilities to play with file and directory paths
- to provide utilities to add and remove files
- It is a retiring module.
- to provide utilities to test files
Explanation: From official docs: reference
- server. start
- server.activate
- server.listen
- server. run
const fs = require('fs'); const os = require('os');
const system = os.platform(); const user = os.userInfo().username;
fs.appendFile('hello.txt', `Hello ${user} on ${system}`, (err) => { if (err) throw err; console.log('The data was appended to file!');}
);
- creates a text file hello.txt and appends customized text
- creates an image file
- console logs system information
- creates a file named data and append numbers
- nodemon start
- start index.js
- node index.js
- node start
- to provide methods to work with requests and responses
- to provide methods to work with files
- to provide methods to work with databases
- to find new file systems
Explanation: From official docs: reference
- It is the current unstable version and is to be avoided.
- It is the version that will be retired soon.
- It is the version with the latest features.
- It is the safest version for long-term support.
- process. stdinfo
- process. stdin
- process. stdout
- process. stderr
Q32. You have a script.js file with the single line of code shown here. What will be the output of executing script.js with the node command?
console.log(arguments);
- ReferenceError: arguments is not defined
- an empty string
- undefined
- an object representing an array that has five elements
- start
- on
- once
- off
Q34. Which special object is an instance of EventEmitter?Which special object is an instance of null?
- process
- Buffer
- root
- require
Q35. What is the command to get a list of available commands for Node.js?What is the command to get a list of available commands for Node.js?
- node index.js -x
- node -v
- node -h
- node index.js -h
Q36. When a request event is received in the HTTP module, what is the type of the first argument passed to that event, usually named req?
- http.IncomingMessage
- http.ServerRequest
- http.ClientRequest
- http.ServerResponse
-
exports, __filename, __dirname -
exports, process, require, module, __filename, __dirname -
exports, module, __filename, __dirname -
exports, require, module, __filename, __dirname
- V8
- c-ares
- libuv
- events
- a C++ file that can have a .node extension and that Node will be able to execute directly.
- a C++ Addon file that is built with node-gyp
- a JSON file that can have a .node extension as well as the .json extension
- a JavaScript file that can have a .node extension as well as the .js extension
- only objects.
- only functions
- only variables and arrays
- functions, objects, arrays, or anything you assign to the module
- os
- util
- cluster
- net
- SSL
- hash
- crypto
- TLS
- const { readFile } = require(fs).promises
- const { readFile } = require(fs)
- const { readFilePromises: readFile } = require(fs)
- const { readFile } = require(promises)
Q44. According to the rules of semantic versioning, what does a release incrementing the third number in an npm version string communicate to users about the release changes?
- Changes are not backwards compatible.
- Changes might not be backward compatible and might break existing code.
- Changes are just bug fixes and no new features were added.
- Changes will add new functionality but will not break any existing code.
- run, examine, put, loop
- read, eval, print, loop
- run, edit, print, loop
- read, extend, print, loop
- .gyprc
- binding.gyp
- gyp.json
- package.gyp
- chai
- jest
- assert
- mocha
Q48. Which core module in Node provides an API to register callbacks to track asynchronous resources created inside a Node.js application?
- cluster
- async_hooks
- dgram
- inspector
Explanation: From official docs: reference
- buffer
- util
- string_decoder
- string_buffer
- v8
- env
- process
- child_process
Explanation: _process is an global object and act like a bridge, the others aren't
- Every Node process runs in a single thread, and all the I/O work is run in that same thread.
- Every Node process gets four threads that it can share between its JavaScript VM and the event loop.
- The event loop is single-threaded, but a JavaScript VM can use multiple threads.
- JavaScript execution in Node.js is single-threaded, but I/O operations are executed using multiple threads.
Explanation: https://www.geeksforgeeks.org/why-node-js-is-a-single-threaded-language/
- Event names must be camelCase strings.
- The emit method allows a arbitrary set of arguments to be passed to the listener functions.
- Any values returned by the listeners for an emitted events are ignored.
- When an event emitter object emits an event, all of the functions attached to that specific event are called synchronously.
Q53. Which core module in Node can you use to compile and run JavaScript code in a sandbox environment?
- sandbox
- buffer
- vm
- v8
Q54. How would you determine the number of cluster instances to start when using the cluster module?
- const numInstances = cluster.instances().length;
- const numInstances = cluster.instances();
- const numInstances = require('os').cpus().length;
- const numInstances = process.cpus().length;
Explanation: From official docs: https://nodejs.org/api/cluster.html#cluster_cluster
Q55. You have to read a large text file, replace some words in it, and write it back to a new file. You know that the memory on your target system is limited. What should you do?
- Use regular expressions directly on the file.
- Use Promises and async/await to offload the task to libuv.
- Copy the file into a database and perform the operations there.
- Use readline together with streams to read and transform and write the file contents line by line.
Explanation: From official docs: https://nodejs.org/api/readline.html#readline_example_read_file_stream_line_by_line
- process
- exports
- setTimeout
- Buffer
Explanation: exports may appear to be global but is not (please see https://nodejs.org/api/globals.html#exports).
- readableStream.pipe(writableStream)
- readableStream.on(pipe, writableStream)
- writableStream.pipe(readableStream)
- writableStream.on(pipe, readableStream)
Q58. How can you convert path segments into a string using the platform-specific separator as a delimiter?
- path.concat
- path.join
- path.format
- path.parse
Explanation: From official docs: reference
- to allow users to make requests to the server
- to insulate Addons from changes in the underlying JavaScript engine
- to execute multi-threaded code in the Node environment
- to provide a quick way for users to create REST APIs
- a locally scoped object that provides information about the current node process
- a global object that provides information about files
- a global object that provides information about the database
- a global object that provides information about the current node process
// File: person.js
exports.name = "Jane";
// File: index.js
const person = require('./person.js');
console.log(person);
-
{'Jane'} -
{ name: 'Jane' } -
{} -
Jane
// File: person.js
exports = "John";
// File: index.js
const person = require('./person.js');
console.log(person);
-
John -
Undefined -
{'John'} -
{}
- yes, through the assert module
- yes, through the debugger module
- yes, through the console module
- no
From the article: Making a Testing Framework in Node.js (Without any External Libraries)
- fail
- doesNotThrow
- deepStrictEqual
- ifError
- promisify
- asyncify
- types
- callbackify
- GlobalError
- TypeError
- RangeError
- AssertionError
- Python
- V8 JavaScript engine
- PHP
- c
Q68. How does it affect the performance of a web application when an execution path contains a CPU-heavy operation, such as calculating a long Fibonacci sequence?
- As Node.js is asynchronous, this is handled by a libuv and a threadpool. The performance will not notably degrade.
- As the application code runs asynchronously within a single thread, the execution will block, accepting no more requests until the operation is completed.
- As Node.js is asynchronous, this is handled by a threadpool and the performance will not notably degrade.
- The current thread will block until the execution is completed and the operating system will spawn new threads to handle incoming requests. This can exhaust the number of allowed threads (255) and degrade performance over time.
- EventLoop
- Libuv
- Google V8
- Express.js
- It indicates success or failure to the client and helps with testing.
- It is not important to have good practices regarding status codes
- Response codes are the only way you can tell what is happening on the server.
- It contains information about the current performance of the server.
- ECMAScript modules cannot be used natively in Node.
- ECMAScript modules can be used natively in Node with the .mjs file extension
- ECMAScript modules can be used natively in Node only by using a compiler like Babel.
- ECMAScript modules can be used natively in Node only by using a bundle like webpack.
- They are an indication of the stability of Nodejs modules and usage recommendations.
- They tell if a feature is ES6 compliant.
- They are a Node command to validate stability of your code.
- They tell if a feature is LTS (Long Term Supported).
- crypto
- chalk
- webpack
- request
Q74. Which DNS module method uses the underlying OS facilities and does not necessarily perform any network communication?
- resolve
- reverse
- lookup
- resolve4
- console.isDate(value)
- util.date(value)
- assert.isDate(value)
- util.types.isDate(value)
- the local .modules folder, then the parents' node_modules folder
- the local node_modules folder, then the parents' node_modules folder
- the .modules folder under the home directory
- a "something.js" file or a "something" folder, which exist on the same level as the requiring file
Q77. An external library has its own codebase and license. It is not managed by the Node.js core team. Which choice is an external library that Node.js uses?
- net
- openssl
- cluster
- events
- to be a system file
- to provide an exact, single representation of the dependency tree
- to serve as a module to export dependencies
- to be a log for the application
const http = require('http');
const hostname = '127.0.0.1';
const port = 3000;
const server = http.createServer((req, res) => {
res.statusCode = 200;
res.setHeader('Content-Type', 'text/plain');
res.end('Hello World\n');
});
server.listen(port, hostname, () => {
console.log(`Server running at http://${hostname}:${port}/`);
});
-
server running at http://127.0.0.1:3000 -
server running at port 3000 -
server running at http://localhost:3000/ -
server running at http://localhost:4000/
- process
- exports
- setTimeout
- Buffer