RxJS Test

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We offer several Front-End tests: JavaScript Online Test React.js Online Test Vue.js Test

The RxJS Test evaluates a candidate's knowledge and understanding of Reactive programming concepts, including observables, operators, subjects, transformation and combination operators, error handling, backpressure and testing.

Covered skills:

Reactive programming
Observables
Operators
Subject
Transformation operators
Combination operators
Error handling
Backpressure
Testing with RxJS
JavaScript Coding

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About the RxJS Assessment Test

The RxJS Test helps recruiters and hiring managers identify qualified candidates from a pool of resumes, and helps in taking objective hiring decisions. It reduces the administrative overhead of interviewing too many candidates and saves time by filtering out unqualified candidates at the first step of the hiring process.

The test screens for the following skills that hiring managers look for in candidates:

Able to understand and use reactive programming concepts effectively
Able to work with observables and perform operations on them
Able to use various operators in RxJS for data transformation
Able to work with subjects to handle multiple subscribers
Able to apply transformation operators on observables
Able to combine observables using combination operators
Able to handle errors effectively in RxJS
Able to deal with backpressure in reactive streams
Able to write tests using RxJS for reactive code
Able to write JavaScript code using RxJS library

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Non-googleable questions

We have a very high focus on the quality of questions that test for on-the-job skills. Every question is non-googleable and we have a very high bar for the level of subject matter experts we onboard to create these questions. We have crawlers to check if any of the questions are leaked online. If/ when a question gets leaked, we get an alert. We change the question for you & let you know.

How we design questions

These are just a small sample from our library of 15,000+ questions. The actual questions on this RxJS Test will be non-googleable.

🧐 Question
Medium Async Await Promises Promises Async-Await Asynchronous Programming	Solve
What will the following code output? A: 24 after 5 seconds and after another 5 seconds, another 24 B: 24 followed by another 24 immediately C: 24 immediately and another 24 after 5 seconds D: After 5 seconds, 24 and 24 E: Undefined F: NaN G: None of these
Medium Bitcoin prices Axios Promises	Solve
Review the following JavaScript code and pick the correct options: Assume that the API returns a successful 200 response code and a JSON object as the response body. What would the value of ‘a’ be after the code is executed?
Medium My Module Scope Javascript Es6 Closure	Solve
What will the output of the following JavaScript code be?
Medium Promise Resolve Promises Async-Await Code Analysis Syntax Understanding	Solve
What does the following code output?
Easy Throw, Try, Async Promises Async-Await Async/await	Solve
What does the following JS code output?

	🧐 Question	🔧 Skill
	Medium Async Await Promises Promises Async-Await Asynchronous Programming	2 mins JavaScript	Solve
What will the following code output? A: 24 after 5 seconds and after another 5 seconds, another 24 B: 24 followed by another 24 immediately C: 24 immediately and another 24 after 5 seconds D: After 5 seconds, 24 and 24 E: Undefined F: NaN G: None of these
	Medium Bitcoin prices Axios Promises	2 mins JavaScript	Solve
Review the following JavaScript code and pick the correct options: Assume that the API returns a successful 200 response code and a JSON object as the response body. What would the value of ‘a’ be after the code is executed?
	Medium My Module Scope Javascript Es6 Closure	2 mins JavaScript	Solve
What will the output of the following JavaScript code be?
	Medium Promise Resolve Promises Async-Await Code Analysis Syntax Understanding	2 mins JavaScript	Solve
What does the following code output?
	Easy Throw, Try, Async Promises Async-Await Async/await	2 mins JavaScript	Solve
What does the following JS code output?

	🧐 Question	🔧 Skill	💪 Difficulty	⌛ Time
	Async Await Promises Promises Async-Await Asynchronous Programming	JavaScript	Medium	2 mins	Solve
What will the following code output? A: 24 after 5 seconds and after another 5 seconds, another 24 B: 24 followed by another 24 immediately C: 24 immediately and another 24 after 5 seconds D: After 5 seconds, 24 and 24 E: Undefined F: NaN G: None of these
	Bitcoin prices Axios Promises	JavaScript	Medium	2 mins	Solve
Review the following JavaScript code and pick the correct options: Assume that the API returns a successful 200 response code and a JSON object as the response body. What would the value of ‘a’ be after the code is executed?
	My Module Scope Javascript Es6 Closure	JavaScript	Medium	2 mins	Solve
What will the output of the following JavaScript code be?
	Promise Resolve Promises Async-Await Code Analysis Syntax Understanding	JavaScript	Medium	2 mins	Solve
What does the following code output?
	Throw, Try, Async Promises Async-Await Async/await	JavaScript	Easy	2 mins	Solve
What does the following JS code output?

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Why you should use Pre-employment RxJS Test?

The RxJS Test makes use of scenario-based questions to test for on-the-job skills as opposed to theoretical knowledge, ensuring that candidates who do well on this screening test have the relavant skills. The questions are designed to covered following on-the-job aspects:

Ability to use Reactive programming concepts in real-world scenarios
Understanding of Observables, how they work and how to create them
Experience with various Operators and their use cases in RxJS
Working knowledge of Subject and its role in event handling
Proficiency in Transformation operators and their applications
Familiarity with Combination operators and their usage in complex scenarios
Ability to handle errors and exceptions in RxJS
Understanding of backpressure and its impact on data flow
Expertise in testing applications using RxJS
Strong coding skills in JavaScript, including the use of RxJS

Once the test is sent to a candidate, the candidate receives a link in email to take the test. For each candidate, you will receive a detailed report with skills breakdown and benchmarks to shortlist the top candidates from your pool.

What topics are covered in the RxJS Test?

Reactive programming: Reactive programming is a programming paradigm that allows developers to build systems that react and respond to changes in the environment. It involves using asynchronous data streams, called observables, and manipulating them using operators to perform various operations. Measurement of this skill in the test helps assess a candidate's ability to work with reactive programming concepts and apply them effectively in their code.

Observables: Observables are a fundamental concept in reactive programming. They represent streams of data that can be observed over time. By subscribing to observables, developers can react to changes in the stream and perform actions accordingly. Measuring this skill in the test helps evaluate a candidate's understanding of observables and their ability to work with them to handle asynchronous events and data.

Operators: Operators in reactive programming are functions that manipulate observable streams and produce new desired output streams. They enable developers to transform, filter, combine, and perform various other operations on observables. Measurement of this skill in the test helps assess a candidate's proficiency in using different operators and their understanding of how to apply them to solve real-world problems effectively.

Subject: A subject is a special type of observable that allows both the emission and consumption of values. It acts as both an observer and an observable, providing a bridge between different parts of an application. Measurement of this skill in the test helps evaluate a candidate's comprehension of subjects and their ability to use them for communication between components or different parts of a system.

Transformation operators: Transformation operators in RxJS enable developers to transform the data emitted by an observable stream into a different format or structure. They help simplify data manipulation and enable logical transformations before consuming the data. Measurement of this skill in the test helps assess a candidate's capability to use transformation operators effectively and understand their diverse range of applications.

Combination operators: Combination operators in RxJS allow developers to combine multiple observables into a single observable stream. They provide various strategies for combining and merging data from multiple sources, enabling powerful composition and coordination of async operations. Measurement of this skill in the test helps evaluate a candidate's ability to work with combination operators and effectively manage complex data flows and dependencies.

Error handling: Error handling in RxJS involves dealing with errors that may occur during asynchronous operations. It includes error propagation, catching, and handling mechanisms to ensure graceful handling of errors and prevent disruptions in the data stream. Measurement of this skill in the test helps gauge a candidate's knowledge and proficiency in implementing error handling techniques in RxJS, ensuring robustness and reliability in their code.

Backpressure: Backpressure is a flow control mechanism in RxJS that allows consumers to control the rate at which they receive data from a producer, preventing overwhelm or resource exhaustion. It ensures that data is consumed at a pace that can be handled effectively. Measurement of this skill in the test helps assess a candidate's understanding of backpressure concepts and their ability to implement appropriate strategies for managing data flow and preventing bottlenecks.

Testing with RxJS: Testing with RxJS involves writing tests for code that utilizes reactive programming and observables. It includes mocking observables, simulating events, and verifying expected behavior. Effective testing helps ensure the correctness and reliability of reactive code. Measurement of this skill in the test helps evaluate a candidate's proficiency in testing RxJS code and their ability to write comprehensive and reliable test cases for reactive applications.

JavaScript Coding: JavaScript coding refers to the ability to write clean, efficient, and maintainable JavaScript code. It involves applying best practices, utilizing language features effectively, and following coding standards. Measurement of this skill in the test helps assess a candidate's JavaScript coding skills and their ability to write high-quality code that is readable, performant, and scalable.

Full list of covered topics

The actual topics of the questions in the final test will depend on your job description and requirements. However, here's a list of topics you can expect the questions for RxJS Test to be based on.

Reactive programming

Observables

Operators

Subject

Transformation operators

Combination operators

Error handling

Backpressure

Testing with RxJS

JavaScript Coding

Creation operators

Filtering operators

Multicasting

Unicast

Hot and cold observables

Multicasting operators

Retries and retriesWhen

Time-based operators

Higher-order observables

Scheduling

Buffering operators

Error handling operators

Conditional operators

Delaying emissions

Distinct operators

Join operators

Partitioning operators

Reducing operators

Scan operator

Serialization operators

Skip and skipLast operators

Take and takeLast operators

Throttle and debounce operators

Windowing operators

Concatenation operators

ForkJoin operator

Merge operator

Race operator

Zip operator

Retry operator

Catch operator

CombineLatest operator

Switch operator

Combinators

Testing marble diagrams

TestScheduler

Asserting operators

Hot and cold observables in testing

Marble testing

Marble diagrams

BehaviorSubject

ReplaySubject

AsyncSubject

BehaviorRelay

PublishSubject

RxJS operators

Promises

Callbacks

Async/Await

ES6 syntax

Arrow functions

Spread and rest operators

Promise.all and Promise.race

Destructuring

Iterator and generators

Classes and inheritance

Modules and import/export

Prototype and prototypal inheritance

High order functions

Functional programming

Closures

Event Loop

DOM manipulation

AJAX and fetch API

Error handling in JavaScript

Debugging techniques

Web storage

Regular expressions

Data types

Scope and hoisting

What roles can I use the RxJS Test for?

Software Developer
Frontend Developer
Full Stack Developer
Web Developer
Angular Developer
UI Developer
JavaScript Developer
Typescript Developer
RxJS Developer
JavaScript Engineer

How is the RxJS Test customized for senior candidates?

For intermediate/ experienced candidates, we customize the assessment questions to include advanced topics and increase the difficulty level of the questions. This might include adding questions on topics like

Ability to apply RxJS concepts to enhance application performance
Experience with handling async operations using Observables
Knowledge of hot and cold observables and their differences
Understanding of multicasting and the role of Subjects in it
Proficiency in using operators like map, filter, and reduce
Familiarity with error handling and retrying mechanisms in RxJS
Ability to implement custom operators and pipelines in RxJS
Expertise in optimizing performance and memory management in RxJS
Knowledge of testing frameworks and methodologies for RxJS
Understanding of JavaScript coding best practices and standards

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Have questions about the RxJS Hiring Test?

What is RXJS Test?

The RxJS Test evaluates a candidate's proficiency in Reactive Programming with RxJS. It's used by recruiters to identify candidates who can handle async operations using Observables and implement optimal performance strategies.

Can I combine rxjs-online-test with JavaScript questions?

Yes, recruiters can request a custom test that combines RxJS and JavaScript skills. To get more details on how we assess JavaScript skills, check our JavaScript Online Test.

What skills are covered in the RXJS Test?

The RxJS Test covers skills like Observables, Operators, Subject, Transformation operators, Combination operators, Error handling, Backpressure, Testing with RxJS, and JavaScript Coding.

How to use RXJS Test in my hiring process?

Use the RxJS Test as a pre-screening tool. Add a link to the assessment in your job post, or invite candidates via email. This helps in identifying skilled candidates early in the process.

Can I test RxJS and JavaScript together in a test?

Yes, you can test both RxJS and JavaScript together. This is recommended for roles that require proficiency in these areas. Check out our JavaScript & React Test for more details.

What are the main Front-End tests?

We offer several Front-End tests:

Can I combine multiple skills into one custom assessment?

Yes, absolutely. Custom assessments are set up based on your job description, and will include questions on all must-have skills you specify. Here's a quick guide on how you can request a custom test.

Do you have any anti-cheating or proctoring features in place?

We have the following anti-cheating features in place:

Non-googleable questions
IP proctoring
Screen proctoring
Web proctoring
Webcam proctoring
Plagiarism detection
Secure browser
Copy paste protection

Read more about the proctoring features.

How do I interpret test scores?

The primary thing to keep in mind is that an assessment is an elimination tool, not a selection tool. A skills assessment is optimized to help you eliminate candidates who are not technically qualified for the role, it is not optimized to help you find the best candidate for the role. So the ideal way to use an assessment is to decide a threshold score (typically 55%, we help you benchmark) and invite all candidates who score above the threshold for the next rounds of interview.

What experience level can I use this test for?

Each Adaface assessment is customized to your job description/ ideal candidate persona (our subject matter experts will pick the right questions for your assessment from our library of 10000+ questions). This assessment can be customized for any experience level.

Does every candidate get the same questions?

Yes, it makes it much easier for you to compare candidates. Options for MCQ questions and the order of questions are randomized. We have anti-cheating/ proctoring features in place. In our enterprise plan, we also have the option to create multiple versions of the same assessment with questions of similar difficulty levels.

I'm a candidate. Can I try a practice test?

No. Unfortunately, we do not support practice tests at the moment. However, you can use our sample questions for practice.

What is the cost of using this test?

You can check out our pricing plans.

Can I get a free trial?

Yes, you can sign up for free and preview this test.

I just moved to a paid plan. How can I request a custom assessment?

Here is a quick guide on how to request a custom assessment on Adaface.

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Along with scorecards that report the performance of the candidate in detail, you also receive a comparative analysis against the company average and industry standards.

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