5 JavaScript Questions and Answers to Test Your Skills

Today we are going to continue learning our beloved JavaScript language, in this edition, we are going to test our skills by answering some JavaScript mini-challenges.

Even though I’ll be giving the answer with an explanation at the end of each question, try to figure it out by yourself first, and then validate your answer against mine.

Question #1: Array Sort Comparison

Consider the following arrays and conditions, what do you think would be the result?

const arr1 = ['a', 'b', 'c']
const arr2 = ['c', 'b', 'a']

console.log(
    arr1.sort() === arr1,
    arr2 === arr2.sort(),
    arr1.sort() === arr2.sort()
)

Answer

true true false

Now that we know the result, let’s explain why. For the first 2 outputs the explanation is rather simple, the sort() method sorts the original array and returns a reference to the same object, so arr1.sort() is actually a reference to the same object as arr1.

For the third output, arr1.sort() === arr2.sort(), even though the elements on each one of the arrays are the same, the === operator will not test the elements of the array but the reference of each object, which in this case is different, and thus returning false.

If you want to know more about array comparisons, check my article Stranger Things, JavaScript Edition, and read Scenario #5: Array equality where I explain with more samples some weird array comparisons with explanations.

#javascript #programming

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5 JavaScript Questions and Answers to Test Your Skills
Sigrid  Farrell

Sigrid Farrell

1623718560

Top 10 Critical Spring Boot Interview Questions and Answers [For Beginners & Experienced]

offers powerful features for the rapid development of deployment-ready applications. It is the most used and best java framework for the development of scalable microservices and web applications.

If you want to become a domain expert, you have come to the right place. We have curated some the most repeatedly asked spring boot interview questions and answers to help you ace the interview.

Basic Spring Boot Interview Questions And Answers

Technical Spring Boot Interview Questions And Answers

Conclusion

#full stack development #interview question answer #spring boot interview questions answer #top spring boot interview questions #top 10 critical spring boot interview questions #answers

Top 130 Android Interview Questions - Crack Technical Interview Now!

Android Interview Questions and Answers from Beginner to Advanced level

DataFlair is committed to provide you all the resources to make you an android professional. We started with android tutorials along with practicals, then we published Real-time android projects along with source code. Now, we come up with frequently asked android interview questions, which will help you in showing expertise in your next interview.

android interview questions

Android Interview Questions – Get ready for your next interview

Android – one of the hottest technologies, which is having a bright future. Get ready to crack your next interview with the following android interview questions. These interview questions start with basic and cover deep concepts along with advanced topics.

Android Interview Questions for Freshers

1. What is Android?

Android is an open-source mobile operating system that is based on the modified versions of Linux kernel. Though it was mainly designed for smartphones, now it is being used for Tablets, Televisions, Smartwatches, and other Android wearables.

2. Who is the inventor of Android Technology?

The inventors of Android Technology are- Andry Rubin, Nick Sears, and Rich Miner.

3. What is the latest version of Android?

The latest version of Android is Android 10.0, known as Android Q. The upcoming major Android release is Android 11, which is the 18th version of Android. [Note: Keep checking the versions, it is as of June 2020.]

4. How many Android versions can you recall right now?

Till now, there are 17 versions of Android, which have their names in alphabetical order. The 18th version of Android is also going to come later this year. The versions of Android are here:

  • Android 1.0 – Its release is 23 September 2008.
  • Android 1.1 – Its release date is 9 February 2009.
  • Android 1.5 – Its name is Cupcake, Released on 27 April 2009.
  • Android 1.6 – Its name is Donut, Released on 15 September 2009.
  • Android 2.0 – Its name is Eclair, Released on 26 October 2009
  • Android 2.2 – Its name is Froyo, Released on 20 May 2010.
  • Android 2.3 – Its name is Gingerbread, Released on 06 December 2010.
  • Android 3.0 – Its name is Honeycomb, Released on 22 February 2011.
  • Android 4.0 – Its name is Ice Cream Sandwich, Released on 18 October 2011.
  • Android 4.1 – Its name is Jelly Bean, Released on 9 July 2012.
  • Android 4.4 – Its name is KitKat, Released on 31 October 2013.
  • Android 5.0 – Its name is Lollipop, Released on 12 November 2014.
  • Android 6.0 – Its name is Marshmallow, Released on 5 October 2015.
  • Android 7.0 – Its name is Nougat, Released on 22 August 2016.
  • Android 8.0 – Its name is Oreo, Released on 21 August 2017.
  • Android 9.0 – Its name is Pie, Released on 6 August 2018.
  • Android 10.0 – Its name is Android Q, Released on 3 September 2019.
  • Android 11.0 – As of now, it is Android 11.

5. Explain the Android Architecture with its components.

This is a popular android developer interview question

Android Architecture consists of 5 components that are-

a. Linux Kernel: It is the foundation of the Android Architecture that resides at the lowest level. It provides the level of abstraction for hardware devices and upper layer components. Linux Kernel also provides various important hardware drivers that act as software interfaces for hardwares like camera, bluetooth, etc.

b. Native Libraries: These are the libraries for Android that are written in C/C++. These libraries are useful to build many core services like ART and HAL. It provides support for core features.

c. Android Runtime: It is an Android Runtime Environment. Android Operating System uses it during the execution of the app. It performs the translation of the application bytecode into the native instructions. The runtime environment of the device then executes these native instructions.

d. Application Framework: Application Framework provides many java classes and interfaces for app development. And it also provides various high-level services. This complete Application framework makes use of Java.

e. Applications: This is the topmost layer of Android Architecture. It provides applications for the end-user, so they can use the android device and compute the tasks.

6. What are the services that the Application framework provides?

The Android application framework has the following key services-

a. Activity Manager: It uses testing and debugging methods.

b. Content provider: It provides the data from application to other layers.

c. Resource Manager: This provides users access to resources.

d. Notification Manager: This gives notification to the users regarding actions taking place in the background.

e. View System: It is the base class for widgets, and it is also responsible for event handling.

7. What are the important features of Linux Kernel?

The important features of the Linux Kernel are as follows:

a. Power Management: Linux Kernel does power management to enhance and improve the battery life of the device.

b. Memory Management: It is useful for the maximum utilization of the available memory of the device.

c. Device Management: It includes managing all the hardware device drivers. It maximizes the utilization of the available resources.

d. Security: It ensures that no application has any such permission that it affects any other application in order to maintain security.

e. Multi-tasking: Multi-tasking provides the users the ease of doing multiple tasks at the same time.

8. What are the building blocks of an Android Application?

This is a popular android interview question for freshers.

The main components of any Android application are- Activity, Services, Content Provider, and Broadcast Receiver. You can understand them as follows:

a. Activity- It is a class that acts as the entry point representing a single screen to the user. It is like a window to show the user interface.

b. Services- Services are the longest-running component that runs in the background.

c. Content Provider- The content provider is an essential component that allows apps to share data between themselves.

d. Broadcast receivers- Broadcast receiver is another most crucial application component. It helps the apps to receive and respond to broadcast messages from the system or some other application.

9. What are the important components of Android Application?

The Components of Android application are listed below:

  1. Widgets
  2. Intents
  3. Views
  4. Notification
  5. Fragments
  6. Layout XML files
  7. Resources

10. What are the widgets?

Widgets are the variations of Broadcast receivers. They are an important part of home screen customization. They often display some data and also allow users to perform actions on them. Mostly they display the app icon on the screen.

11. Can you name some types of widgets?

Mentioned below are the types of widgets-

a. Informative Widgets: These widgets show some important information. Like, the clock widget or a weather widget.

b. Collective Widgets: They are the collection of some types of elements. For example, a music widget that lets us change, skip, or forward the song.

c. Control Widgets: These widgets help us control the actions within the application through it. Like an email widget that helps check the recent mails.

d. Hybrid Widgets: Hybrid widgets are those that consist of at least two or more types of widgets.

12. What are Intents?

Intents are an important part of Android Applications. They enable communication between components of the same application as well as separate applications. The Intent signals the Android system about a certain event that has occurred.

13. Explain the types of intents briefly?

Intent is of three types that are-

a. Implicit Intents: Implicit intents are those in which there is no description of the component name but only the action.

b. Explicit Intents: In explicit intents, the target component is present by declaring the name of the component.

c. Pending Intents: These are those intents that act as a shield over the Intent objects. It covers the intent objects and grants permission to the external app components to access them.

14. What is a View?

A view is an important building block that helps in designing the user interface of the application. It can be a rectangular box or a circular shape, for example, Text View, Edit Text, Buttons, etc. Views occupy a certain area of the screen, and it is also responsible for event handling. A view is the superclass of all the graphical user interface components.

15. What do you understand by View Group?

It is the subclass of the ViewClass. It gives an invisible container to hold layouts or views. You can understand view groups as special views that are capable of holding other views, that are Child View.

16. What do you understand about Shared Preferences?

It is a simple mechanism for data storage in Android. In this, there is no need to create files, and using APIs, it stores the data in XML files. It stores the data in the pair of key-values. SharedPreferences class lets the user save the values and retrieve them when required. Using SharedPreferences we can save primitive data like- boolean, float, integer, string and long.

17. What is a Notification?

A notification is just like a message that shows up outside the Application UI to provide reminders to the users. They remind the user about a message received, or some other timely information from the app.

18. Give names of Notification types.

There are three types of notifications namely-

a. Toast Notification- This notification is the one that fades away sometime after it pops up.

b. Status Notification- This notification stays till the user takes some action on it.

c. Dialog Notification- This notification is the result of an Active Activity.

19. What are fragments?

A fragment is a part of the complete user interface. These are present in Activity, and an activity can have one or more fragments at the same time. We can reuse a fragment in multiple activities as well.

20. What are the types of fragments?

There are three types of fragments that are: Single Fragment, List Fragment, Fragment Transactions.

  1. Single Transactions can only show a single view for the user.
  2. List Fragments have a special list view feature that provides a list from which the user can select one.
  3. Fragment Transactions are helpful for the transition between one fragment to the other.

Frequently asked Android Interview Questions and Answers

21. What are Layout XML files?

Layout XML files contain the structure for the user interface of the application. The XML file also contains various different layouts and views, and they also specify various GUI components that are there in Activity or fragments.

22. What are Resources in Android Application?

The resources in Android Apps defines images, texts, strings, colors, etc. Everything in resources directory is referenced in the source code of the app so that we can use them.

23. Can you develop Android Apps with languages other than Java? If so, name some.

Yes, there are many languages that we can work with, for the development of Android Applications. To name some, I would say Java, Python, C, C++, Kotlin, C#, Corona/LUA.

24. What are the states of the Activity Lifecycle?

Activity lifecycle has the following four stages-

a. Running State: As soon as the activity starts, it is the first state.

b. Paused State: When some other activity starts without closing the previous one, the running activity turns into the Paused state.

c. Resume State: When the activity opens again after being in pause state, it comes into the Resume State.

d. Stopped State: When the user closes the application or stops using it, the activity goes to the Stopped state.

25. What are some methods of Activity?

The methods of Activity are as follows:

  • onCreate()
  • onStart()
  • onPause()
  • onRestart()
  • onResume()
  • onStop()
  • onDestroy()

26. How can you launch an activity in Android?

We launch an activity using Intents. For this we need to use intent as follows:

  1. ntent intent_name= new Intent(this, Activity_name.class);
  2. startActivity(intent_name);

27. What is the service lifecycle?

There are two states of a service that are-

a. Started State: This is when the service starts its execution. A Services come in start state only through the startService() method.

b. Bounded State: A service is in the bounded state when it calls the method bindService().

28. What are some methods of Services?

The methods of service are as follows-

  • onStartCommand()
  • onBind()
  • onCreate()
  • onUnbind()
  • onDestroy()
  • onRebind()

29. What are the types of Broadcast?

Broadcasts are of two types that are-

a. Ordered Broadcast: Ordered broadcasts are Synchronous and work in a proper order. It decides the order by using the priority assigned to the broadcasts.

b. Normal Broadcast: These are asynchronous and unordered. They are more efficient as they run unorderly and all at once. But, they lack full utilization of the results.

30. What are useful impotent folders in Android?

The impotent folders in an Android application are-

  1. build.xml- It is responsible for the build of Android applications.
  2. bin/ – The bin folder works as a staging area to wrap the files packages into the APK.
  3. src/ – The src is a folder where all the source files of the project are present.
  4. res/ – The res is the resource folder that stores values of the resources that are used in the application. These resources can be colors, styles, strings, dimensions, etc.
  5. assets/ – It provides a facility to include files like text, XML, fonts, music, and video in the Android application.

31. What are the important files for Android Application when working on Android Studio?

This is an important android studio interview question

There are following three files that we need to work on for an application to work-

a. The AndroidManifest.xml file: It has all the information about the application.

b. The MainActivity.java file: It is the app file that actually gets converted to the dalvik executable and runs the application. It is written in java.

c. The Activity_main.xml file: It is the layout file that is available in the res/layout directory. It is another mostly used file while developing the application.

32. Which database do you use for Android Application development?

The database that we use for Android Applications is SQLite. It is because SQLite is lightweight and specially developed for Android Apps. SQLite works the same way as SQL using the same commands.

33. Tell us some features of Android OS.

The best features of Android include-

  1. Multi-tasking
  2. Support for a great range of languages
  3. Support for split-screen
  4. High connectivity with 5G support
  5. Motion Control

34. Why did you learn Android development?

Learning Android Studio is a good idea because of the following-

  1. It has a low application development cost.
  2. It is an open-source platform.
  3. It has multi-platform support as well as Multi-carrier support.
  4. It is open for customizations.
  5. Android is a largely used operating system throughout the world.

35. What are the different ways of storage supported in Android?

The various storage ways supported in Android are as follows:

  1. Shared Preference
  2. Internal Storage
  3. External Storage
  4. SQLite Databases
  5. Network Connection

36. What are layouts?

Layout is nothing but arrangements of elements on the device screen. These elements can be images, tests, videos, anything. They basically define the structure of the Android user interface to make it user friendly.

37. How many layout types are there?

The type of layouts used in Android Apps are as follows:

  1. Linear Layout
  2. Relative Layout
  3. Constraint Layout
  4. Table Layout
  5. Frame Layout
  6. Absolute Layout
  7. Scrollview layout

38. What is an APK?

An APK stands for Android Package that is a file format of Android Applications. Android OS uses this package for the distribution and installation of the Android Application.

39. What is an Android Manifest file?

The manifest file describes all the essential information about the project application for build tools, Android operating system, and google play. This file is a must for every Android project that we develop, and it is present in the root of the project source set.

#android tutorials #android basic interview questions #android basic questions #android developer interview questions #android interview question and answer #android interview questions #android interview questions for experienced #android interview questions for fresher

Armando  Bruen

Armando Bruen

1595911080

5 JavaScript Questions and Answers to Test Your Skills

Feature Image

Today we are going to continue learning our beloved JavaScript language, in this edition, we are going to test our skills by answering some JavaScript mini-challenges.

Even though I’ll be giving the answer with an explanation at the end of each question, try to figure it out by yourself first, and then validate your answer against mine.

Question #1: Array Sort Comparison

Consider the following arrays and conditions, what do you think would be the result?

const arr1 = ['a', 'b', 'c']
const arr2 = ['c', 'b', 'a']

console.log(
    arr1.sort() === arr1,
    arr2 === arr2.sort(),
    arr1.sort() === arr2.sort()
)

Answer

true true false

Now that we know the result, let’s explain why. For the first 2 outputs the explanation is rather simple, the sort() method sorts the original array and returns a reference to the same object, so arr1.sort() is actually a reference to the same object as arr1.

For the third output, arr1.sort() === arr2.sort(), even though the elements on each one of the arrays are the same, the === operator will not test the elements of the array but the reference of each object, which in this case is different, and thus returning false.

If you want to know more about array comparisons, check my article Stranger Things, JavaScript Edition, and read Scenario #5: Array equality where I explain with more samples some weird array comparisons with explanations.


Question #2: Object Mutability

For this scenario, I’d like to simulate an object which represents an author, and information about his website. We will then use the method Object.freeze() so it can’t be changed, and we will put it to the test. What do you think will be the result?

const author = {
  name: 'Juan',
  website: {
    type: 'blog',
    url: 'https://livecodestream.dev',
  }
}

Object.freeze(author)

author.website.type = 'test'

console.log(author.website.type)

#javascript #questions #programming

Tamia  Walter

Tamia Walter

1596754901

Testing Microservices Applications

The shift towards microservices and modular applications makes testing more important and more challenging at the same time. You have to make sure that the microservices running in containers perform well and as intended, but you can no longer rely on conventional testing strategies to get the job done.

This is where new testing approaches are needed. Testing your microservices applications require the right approach, a suitable set of tools, and immense attention to details. This article will guide you through the process of testing your microservices and talk about the challenges you will have to overcome along the way. Let’s get started, shall we?

A Brave New World

Traditionally, testing a monolith application meant configuring a test environment and setting up all of the application components in a way that matched the production environment. It took time to set up the testing environment, and there were a lot of complexities around the process.

Testing also requires the application to run in full. It is not possible to test monolith apps on a per-component basis, mainly because there is usually a base code that ties everything together, and the app is designed to run as a complete app to work properly.

Microservices running in containers offer one particular advantage: universal compatibility. You don’t have to match the testing environment with the deployment architecture exactly, and you can get away with testing individual components rather than the full app in some situations.

Of course, you will have to embrace the new cloud-native approach across the pipeline. Rather than creating critical dependencies between microservices, you need to treat each one as a semi-independent module.

The only monolith or centralized portion of the application is the database, but this too is an easy challenge to overcome. As long as you have a persistent database running on your test environment, you can perform tests at any time.

Keep in mind that there are additional things to focus on when testing microservices.

  • Microservices rely on network communications to talk to each other, so network reliability and requirements must be part of the testing.
  • Automation and infrastructure elements are now added as codes, and you have to make sure that they also run properly when microservices are pushed through the pipeline
  • While containerization is universal, you still have to pay attention to specific dependencies and create a testing strategy that allows for those dependencies to be included

Test containers are the method of choice for many developers. Unlike monolith apps, which lets you use stubs and mocks for testing, microservices need to be tested in test containers. Many CI/CD pipelines actually integrate production microservices as part of the testing process.

Contract Testing as an Approach

As mentioned before, there are many ways to test microservices effectively, but the one approach that developers now use reliably is contract testing. Loosely coupled microservices can be tested in an effective and efficient way using contract testing, mainly because this testing approach focuses on contracts; in other words, it focuses on how components or microservices communicate with each other.

Syntax and semantics construct how components communicate with each other. By defining syntax and semantics in a standardized way and testing microservices based on their ability to generate the right message formats and meet behavioral expectations, you can rest assured knowing that the microservices will behave as intended when deployed.

Ways to Test Microservices

It is easy to fall into the trap of making testing microservices complicated, but there are ways to avoid this problem. Testing microservices doesn’t have to be complicated at all when you have the right strategy in place.

There are several ways to test microservices too, including:

  • Unit testing: Which allows developers to test microservices in a granular way. It doesn’t limit testing to individual microservices, but rather allows developers to take a more granular approach such as testing individual features or runtimes.
  • Integration testing: Which handles the testing of microservices in an interactive way. Microservices still need to work with each other when they are deployed, and integration testing is a key process in making sure that they do.
  • End-to-end testing: Which⁠—as the name suggests⁠—tests microservices as a complete app. This type of testing enables the testing of features, UI, communications, and other components that construct the app.

What’s important to note is the fact that these testing approaches allow for asynchronous testing. After all, asynchronous development is what makes developing microservices very appealing in the first place. By allowing for asynchronous testing, you can also make sure that components or microservices can be updated independently to one another.

#blog #microservices #testing #caylent #contract testing #end-to-end testing #hoverfly #integration testing #microservices #microservices architecture #pact #testing #unit testing #vagrant #vcr

Jamal  Lemke

Jamal Lemke

1603580400

Ten Principles For Agile Testers

In the previous blog we saw that what exactly is Agile testing and in this blog we will see in introduction to Principles For Agile Testers.

What is an Agile tester?

  • So get into the principles for Agile testers we first need to know what is an Agile tester? A professional tester who is not scared of change has knowledge about technical and business aspects as well and understands the concept of using tests to document requirements to drive development is an Agile tester.
  • Now let’s see what are in ten principles for Agile testers:
  • Provide continuous feedback.
  • Deliver value to the customer.
  • Enable face-to-face communication.
  • Have courage.
  • Keep it simple.
  • Practice continuous improvement.
  • Respond to change.
  • Self-organize.
  • Focus on people.
  • Enjoy

Provide Continuous Feedback

  • Continuous feedback is the key to agile testing success. By providing feedback we can improve and not make the same mistakes again and again. The main aim is to learn from your mistakes. Testers should help product owners or customers visualize requirements for the stories. Their feedbacks helps in designing the test cases early in the software life cycle. As retrospectives are an important part of the Agile process, providing feedback in it is also helpful. It is one of the most important principles for Agile testers.

Deliver Value to the Customer

  • As a tester, it’s your responsibility to tell customers which really is an important function and which is not. The testers help them identify the main functionality instead of just some cool features. The main focus is to try and deliver critical functionality and enhance it later. Critical functionalities should be worked on first as after seeing them implemented, customers can see what enhancements they want. Testing should work on corner cases but should not forget about the happy path of the service. As we get involved in testing it is possible to get involved in corner cases so much that we miss the core functionality. So, we need to maintain a balance between them.

Enable Face-to-Face Communication

  • Good communication is the key to success. Agile’s success is totally dependent upon communication. Whether it is between customer and developer or between developers and the testers all communication is very important. Testers should look for unique ways to communicate. Teams may be working in geographically divided. But it should not hinder communications between the teams.
  • Testers should never get in the way of any direct customer-developer communication but should help to make sure that communication happens. If a tester finds out that the developer has some confusion regarding the requirements. It’s the responsibility of the tester to set up a meeting between the developer and the business.
  • The testers understand the story from the customer’s perspective and from the developers’ technical angle as well. The tester should be able to communicate both ways, that’s why it’s in testers’ best interest to be good at communicating, as they need to do it more than any other team member. Testers act as a bridge between customers and developers.

Have Courage

  • The testers should have the courage to speak their minds. They should not be intimidated by anyone. If they find any issue they should report it. If they see any gap in the business requirements they should discuss it.
  • The testers should be comfortable in asking customers for examples or developers for help. Asking for examples is the best way for getting the real-world use case of the services. In Agile anyone can perform any task. So, a developer can help a tester in testing some particular scenario. And a tester can help the developers in debugging an issue ass well.
  • Testers should not be scared to fail but should learn from their mistake. It’s natural to make some mistakes but we should always learn from them and improve ourselves.

#api testing #integration testing #quality assurance (qa) #testing #unit testing #agile #agile teams #agile transformation #agiledeveloper #automation #automation testing #testing skills