Angular 2 Interview Questions and Answers

Angular 2 Interview Questions and Answers

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Best Angular 2 Interview Questions and Answers

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Q1) How would you explain Angular 2?

Answer: Angular 2 is the promoted and progressed version of AngularJS, which is a JavaScript framework and it was industrialized by Google. It is used for the construction of mobile applications and single-page web.
Number of Components of in Angular 2 are scopes, directives, and controllers, templates, metadata, class, etc.

Q2) Explain the term directives?

Answer: They represent prolonged HTML attributes. They are the most significant features of Angular apps. Top 3 directives used are Components, Attribute and Structural.

Q3) Explain the use of tsconfig.json?

Answer: It is used to postulate the files at root level and the options of compiler essential for compiling a TypeScript project.

Q4) Explain routing?

Answer: The Router allows viewers to circumnavigate from one page to the next. Routing supports users on the basis of the option selected on the main web page.

Q5) Are there any security threats in angular 2 you should be aware of?

Answer: Threats emerge when you do something not legit. For example, Injecting dynamic content of HTML etc. To avoid these, you should cleanse external HTML, in the application avoid using external URLs, AOT compilation should be used, restrict API and prevent XSRF attacks.

Q6) If the path is non-existent, how would you redirect to 404?

Answer: You can always configure a URL that redirects to the succeeding URL. This is also handled to address problems like “404 Not Found”. To go through history pages, location services can be used.

Q7) What is the provision to handle Angular 2 errors?

Answer: Every Angular 2 app can handle errors as they have the choice to find error. Using catch library ReactJS as well as catch function, it can be easily done.

Q8) Explain Traceur compiler?

Answer: It takes classes and other features like generators from ECMAScript edition 6. It compiles them into JavaScript ES5 and it runs on browser. Developers use the code of advanced version with many features encouraging design forms.

Q9) Explain dependency injection?

Answer: Angular allows declared dependencies assigned to a class while instantiation. For injection of a service, injectable service should be registered after creation of it.

Q10) Explain lazy loading?

Answer: Using lazy loading, components of JS are overloaded asynchronously when activation occurs on a precise path.

Q11) Explain pipes?

Pipes is a feature used in Angular 2 and onward versions. It is used to design custom pipes. A pipe is used to input data and convert it into the desired output.

Q12) Why is lazy loading used in angular 2?

Answer: This technique allows developers loading of different codes on demand. Let us suppose, you ware working with a retail application and it has diverse departments such as garments, electronics an so on. Application starts running slow when all the sections are loaded all at once. With lazy loading, only the parts required by user are loaded and hence application load faster than before.

Q13) Explain the benefits of unit testing?

Answer: Use of Unit testing comes when you want to comprehend the fundamental concepts related to test cases of Angular 2. When you are trying to upgrade them to Angular projects, it can be easily found which test has failed.
Following are the benefits of unit testing-

• It exposes the design errors
• It helps in analyzing the code behavior
• It acts as a guard against breaking changes
• It also allows the refactoring
• This test helps the developers in their work

Q14) What is the process of singleton service?

Answer: After importing injectable member from ‘@angular/core’, HttpModule is imported along with Http as well as Response members.
Once that is done @Injectable() decorator is added.

Q15) What is component creation process?

Answer:

• Top level component is imported using ‘@angular/core’;
• @ is used for component description.
• Instances are created of @Directive, @RouterConfig and @Injectable, etc.
• Meta-data is added (selector, styles, providers, template)
• Component is Exported
• Component is Bootstrapped

Q16) What are event emitters?

Answer: A change propagates to its children from the component itself. To reflect the same change to the parentsomethingChanged.emit(v1) where v1 is valued can also be used for emitting any event. This is done in the setter while value change happens in the class.

Q17) How is component is different from directive?

Answer: They both have different annotations, for components, @Component is used and for the directive, @Directive is used. The component is used for UI widgets. The directive is used for designing reusable components. One component is applicable for one DOM element whereas many directives are applicable for one DOM elements. The view is used as @View in a component while directive makes no use of View.

Q18) Explain Typings?

Answer: It is used to handle definitions of typescript. To manage the typing type definition manager is used. It permits the typescript compiler for easy use in class as well as properties. Installation of typing becomes easy with typing commands.

Q19) What is the declaration of a global variable?

Answer: The most common way is putting variables in the file then export them. Import statement is used to use global variables.

Q20) Is Angular 2 better than Angular JS?

Answer: It is better than angular JS because of the following reasons:

• Easy to Learn
• Dependency Injection is very simple
• A platform as well as language
• Better-quality Speed with Performance
• Cross-platform and modular
• Supple Routing and Lazy Loading
• Assistances of ES6 as well as Typescript.

Q21) Can data be passed into components?

Answer: There is a property binding trait for this. For binding data and components, creation of property bind is required. Using decorator @Input() you can create input binding.

Q22) How are observables different from promises?

Answer:

Q23) Explain hooks?

Answer: These are functions called on specific phases of a component’s life. They are required if app is built on the component architecture. For example, $onInit. These are some properties pre-defined in Angular and they are exposed on module controllers.

Q24) How can you create services?

Answer:

• First thing, injectable member is imported.
• Decorator used is @Injectable
• Service class will be exported

Q25) Explain custom Pipes?

Custom pipes are pipes created by the user. You can decide the transform function working with custom pipe, pass parameters to it, return value from it.

Q26) What is styleUrls, styles?

Answer: StyleUrls are used to affect the template element style. The built-in features in the Decorator help developers to condense styles as part of components. Style and styleUrls represent arrays, many definitions can be applied for every position.

Q27) Explain CLI?

CLI or command line interface is used for building angular apps. It is helpful to construct & initiate a project rapidly.

Q28) How is @injectable() different from @inject()?

Answer:

Q29) Explain AOT compilation?

Answer: AOT or Ahead-of-Time (AOT) is a compiler is used to convert HTML or TypeScript program lines into JavaScript during the phase of building prior to the browser downloading and running code.
Other benefits of AOT are:

• Quick rendering
• Slighter asynchronous requests
• Reduced download size
• Detects errors effortlessly
• Better security and protection

Q30) Explain AOT advantages as well as limitations?

Answer:
 Advantages

• Quick download
• Faster rendering
• Decreases Http Requests
• Finds errors in the building level

Disadvantages

• Cannot work along with file when it is not HTML or CSS
• Must uphold bootstrap file AOT form
• Must clean-up prior to the compilation process

Q31) How will requestAnimationFrame undefined error is solved?

Answer: This is a worldwide server running problem. The best answer for this is to look for requestAnimationFrame then ensure that it’s only being called when the client is in a browser and not the server.

Q32) What is the process for writing console.log statements into a file?

Answer: You can use “logging” flags from the command line. You can make sure with console.log() that data is locked internally with console.log ().
Lock file here is called chrome_debug.log. It is located in the directory.

Q33) Can you check for installed CLI?

Answer:

• First, you should make sure that at least node installation is done. Then CLI installation can be checked.
• Use cmd and Open prompt.
• Type node -v
• Type npm -v
• It will ensure the node is installed.
• Type ng -v now

Q34) Explain directive Router-link?

Answer: This one is used to navigate from any view. It works directly as a user is doing application tasks. This link can right away be available from the browser. Navigation is done based on user action. This directive provides control to the elements of the anchor tag.

Q35) Can you improve Angular2’s performance?

Answer: You can do that using OnPush, TrackBy, Lazy Loading, avoiding value computation in the template, change detection should be disabled.

Q36) How is constructor different from ngOnInit?

Answer:

• A default method of a class is Constructor and it is automatically called at the creation of a new object.
• ngOnInit represents a hook of the life cycle in Angular and it indicates the component completion.
• Also for inject, dependencies constructor is used.
• ngOnlnit is useful when initialization logic is to be performed.

Q37) Explain hidden property?

Answer: This is a specific case binding trait to hide property. You can compare it tong-show and also to ng-hide, nonetheless, it is more powerful.

Q38) Explain @input, @output?

Answer: These are decorators. @Input is useful in the binding of property inside one component child to obtain parent value. @output is used for property binding in component to direct data of component child to parent.

Q39) From backend how will you show error message in angular2?

Answer: For this, the error message is set equal to a variable. These are angular variables. Then you can check if this variable is existing and conform if you wish to show it.

Q40) Explain priming2?

Answer: It is a UI component used in Angular. It’s very simple and lightweight but also very powerful as well as improved for a receptive touch of cross-browser.

Q41) Can you improve the application to have better performance?

Answer: We can do that using the following steps:

• Using AOT compilation.
• Using lazy loading and not completely bundled app.
• Sidestep nonessential import statements.
• Eliminate unused plus redundant libraries from 3rd party.
• Application dependencies should be removed when not required.

Q42) Angular 2 is Object-Oriented or not?

Answer: Yes, it is a proper object-oriented framework.

Q43) Explain tree shaking?

Answer: To eliminate dead code this concept is used in projects. If some code is not referenced but still written in the project, you can drop it here. It is helpful in eliminating unused modules while the building process. It also makes applications lightweight.

Q44) Can you change input written in lowercase as well as uppercase?

Answer: Yes. The filter can be used to do that. Lowercase and uppercase letters can be converted.

Q45) Explain custom typings so that editor warnings can be avoided?

Answer: For that, you need to spread the type definition of an external library. Without making any changes to node_modules, you need to create a folder with name “custom_typings”. This is the place where you can keep customized type definitions.

Q46) Explain injectable?

Answer: A very significant application, Injectable is an indispensable component providing modularity. They are associated through injector type.

Q47) Explain shadow DOM?

Answer: Shadow DOM is an important portion of Web Components and it enables style encapsulation. It also helps to hide DOM logic. Along with it, you can use scoped styles lacking showcasing to the outer world.

Q48) When was Angular 2 released?

2016.

Q49) Explain external CSS style loading?

Answer: For that, you can change view encapsulation and it presents styles denoting “bleed into”.

Q50) How is templateUrl different from a template?

Answer: templateUrl is used to define external templates in HTML. Template is used to specify Inline templates with template.