JavaScript and Node.js Online Test

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About the test

The JavaScript and Node.js online test assesses candidates' knowledge of JavaScript language and specific Node.js features.

It's an ideal test for pre-employment screening. A good Node.js developer needs to be able not only to solve problems using Node.js but also to be familiar with the Node.js ecosystem.

This online test requires candidates to solve coding problems in JavaScript and Node.js.

Sample public questions

Easy
20 min
code
Public
AI-resistant
JavaScript
Arrays
Iteration

Your company is analyzing malware which targets numerical record files.

The malware uses a sliding window over the array of numbers in a file, and tries to match the following pattern:

Tl, -, -, X, -, -, -, Tr

The entire window is moved so that 'X' passes through all the values and is compared to the numbers at the 'Tl' and 'Tr' locations, which are positioned at a constant offset to 'X'.

The malware has the following rules:

  • If the value at the 'Tl' or 'Tr' position of the pattern is bigger or equal to the value at the 'X’ position, the malware replaces the value at 'X' with 0.
  • If the value at the 'Tl' or 'Tr' offset is out of bounds, then the value at 'X' is only compared to the other existing value.
  • The record is processed in two stages: first, all the positions that should be set to 0 are located, using the original values for comparison. Only after all positions have been identified do they get set to 0.

For example, if the values in a record file are the following:

[1, 2, 0, 5, 0, 2, 4, 3, 3, 3]

The expected values after the malware runs are:

[1, 0, 0, 5, 0, 0, 0, 3, 3, 0]

In this example, both '2's, the '4' and the last '3' were replaced by 0.

Implement the simulate function so that the malware behavior is replicated for further study.

Hard
10 min
code
Public
Node.js
Async-Await
Asynchronous Calls
Promise

A company uses a Node.js application that checks several data sources for requested information. Since each request to a data source is performance heavy, the application should try to check the next source only if the request failed at the current data source. That functionality was extracted into the firstSuccessfulPromise function.

The firstSuccessfulPromise function accepts an array of Promises as a promiseArray parameter. The function should return a Promise which should resolve to the first successful result from the promiseArray.

If no Promise from the promiseArray returns successfully, the function should return undefined.

For example, if the following code is executed:

firstSuccessfulPromise([new Promise((resolve, reject) => reject()), 
              new Promise((resolve, reject) => resolve("Success!"))])
  .then(result => console.log(result));

It should print "Success!".

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73 more premium JavaScript and Node.js questions

Positive Numbers, Truthy Expressions, Fahrenheit Converter, Shopping Cart, Weather Data, File Exists, Retry Request, Run Sequentially, Stream Transform, Function Wrapper, Package Declaration, Add Id, Hash Bug, Game Action, Arrange Promises, Unique Numbers, Load URL, Photon Frequency, Confirm, Segment, Height, Product Rating, Validation, Array Search, Screen, Username, Snapshot, Scale Font Size, Hide Button, A Tag, Hobbies, Loading Bar, Double, Table of Names, Filter, Reorder, Trading Data Paging, New Folder, Chain Link, Node, Special Actions, Log Parser, Log Patch, Cards, Increase Priority, Ticket Transition, Post Comment, Friend, Vectors, Date Transform, Construction Game, Calories Burned, Students, Digital Flasks, Airport Networks, Company Stock, Planet Search, Shipping, Tax Calculator, Numbers To Text, Max Sum, Launch Time, Color Codes, Row Appender, Timer, Read Write Execute, Paper Strip, Memory Game, Circuit Simulator, Chemical Machine, Flimsy Ladder, Jogging App, Paragraph.

Skills and topics tested

  • JavaScript
  • Closures
  • Language
  • Node.js
  • Modules
  • Events
  • Asynchronous Programming
  • Async-Await
  • Promise
  • JSON
  • Stream
  • Exceptions
  • NPM
  • Event Loop
  • Bug Fixing
  • Event Emitter
  • Algorithmic Thinking
  • Dictionary
  • Ajax
  • HTTP
  • Arrays
  • Dialog Box
  • Event Handling
  • Arithmetic
  • Objects
  • Attribute Manipulation
  • DOM Manipulation
  • Forms
  • Recursion
  • Classes
  • ECMAScript 2015
  • Regex
  • Strings
  • Styling
  • Asynchronous Calls
  • Iteration
  • HTML5
  • Pagination
  • Serialization
  • Sorting
  • Linked List
  • Tree
  • XML
  • Monkey Patching
  • Content Manipulation
  • Graphs
  • 2D Array
  • AI Code Review
  • Conditional Statements
  • Loops
  • Conditions
  • Timing Events
  • Associative Arrays
  • Callback

For job roles

  • Back-End Developer
  • JavaScript Developer
  • Node.js Developer

Sample candidate report

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Simple, straight-forward technical testing

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Product reviews

G2 - Crowd Badge
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Capterra - 4.5 Stars
Capterra - Shortlist (2023)

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