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Angular.js 2 interview questions

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Interview questions for your next interview

Question
Why should we use Angular 2 instead of React, Angular 1, backbone etc?
Answer
Using or not using Angular 2 for project depends on scope of your app. Using Angular 2 would help in cases where we want to create single page AJAX application to support mobile and desktop browsers.
Question
What problem is Angular 2 trying to solve?
Answer
Angular 2 is providing MVVM and MVC architecture for browser Javascript code management. It provides modules for isolating application code, routing between controllers, dynamic template loading and extending HTML markups in terms of components and directives.

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Question
What benefits does .ts provide over legacy JS?
Answer
TypeScript provides all qualities and functionalities of Javascript; other than this it provides extended qualities such as static type casting which improve code execution efficiency. TS is compiled to Javascript before running on browser, which improve page render time etc.
Question
Why are decorators used in Angular 2?
Answer
Decorators are used as identifier of class or type of object that is being created in TypeScript. Angular 2 identifies class below decorator call as definition of class and extend decorator specific properties with class definition.
Question
What is root module for Angular 2 and what are its parameters?
Answer
@ngModule is the root module or class for an angular application. It is identified with decorator @ngModule and identifies the entry point of an application. It takes an object as parameter whose properties are imports, exports, declarations, providers, bootstrap.
Question
How does angular 2 keep track of two-way data binding?
Answer
Angular 2 runs script for checking model stored values against displayed HTML values once per Javascript event cycle for whole application tree. If any value has changed on either side it replace the value to make them consistent. [(ngModel)]=”foo” is used as two-way binding attribute.
Question
What limits the number of two-way binding attributes in Angular 2?
Answer
Too many two-way binding attributes can cause performance concerns in application. Each data binding pushes an event in Javascript event loop messages que, and pushing too many messages can block event loop and browser window.
Question
How is using two-way data binding encouraged in Angular 2?
Answer
Using two-way binding within the scope of component only is encouraged. If a model receive too many inputs, its resolution can create inaccuracy.
Question
What is difference between component and directive in Angular 2?
Answer
Component is a directive with template. Directive doesn’t have a template, while components have. Directives are identified with @Directive decorator while components are identified as @Component.
Question
How can we bind a variable with DOM element in Angular 2?
Answer
Angular 2 provides this feature with ‘#foo’ syntax. A variable resembles Javascript DOM element and can be referenced in controller as well as DOM. i.e.

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Question
What can be considered as replacement of $watch in Angular 2?
Answer
ngOnChanges lifecycle hook can be considered as replacement of $watch in Angular 1. This hook is invoked every time angular identifies a change in components input model with two parameters; currentValue, oldValue.
Question
What are pipes in Angular 2?
Answer
Pipes are used in templates to convert output to user friendly and readable form within interpolation braces i.e. {{ release | date }}. The ‘|’ is denoted as pipe.
Question
Can we automate porting Angular 1 code to Angular 2?
Answer
No, currently there is no such tool available. Porting Angular 1 code to Angular 2 code will include side by side manual conversion of Angular 1 directives to Angular 2 components because they are two different approaches to solve the same problem and hence two different frameworks.
Question
Which Angular 2 directive can be used for internationalization?
Answer
i18n is the Angular 2 directive that is used for internationalization i.e. conversion of static HTML text in multiple languages.
Question
What is Host Decorators in Angular 2?
Answer
Host decorators bind properties of component with UI element values. The properties inside component class definition decorated with @HostBinding can be accessed in template from assigned property i.e. @HostBinding() title = ‘My Title’.
Question
What are Observables in Angular2
Answer
Observables in Angular 2 are similar to promises but with major differences that make them better. Observables handle multiple values over time which makes them a good candidate for working with real-time data. Observables can also be cancelled and this gives a better control when working with in-flow of values from a stream. Observables is an ES7 feature which means you need to make use of an external library to use it today. For example, RxJS - https://github.com/Reactive-Extensions/RxJS.

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