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In order to set headers for every request in ANGULAR 7, HTMLHttpRequest is used. There is a number of benefits such as testability features, TYPES request, request and response interception, observable APIs and streamlined error HANDLING that is associated with, XMLHttpRequest.

Angular 7 has two CORE DEPENDENCIES namely RxJS and TypeScript

• RxJS 6.3 – Angular 7 FRAMEWORK uses RxJS version 6.3.
• TypeScript- Angular 7 framework uses TypeScript version 3.1

Structural directive

The main function of the structural directive is to shape and re-shape the HTML LAYOUT, and DOM’s structure. The MODIFICATION and customization of HTML layout are done by ADDING, removing and manipulating the selected HTML elements.

The attribute directive has its own layout view and styles because it has a single component on a host ELEMENT but it supports multiple directives.

In Angular 7, templates are written with the help of HTML that contains Angular JS specification elements and ATTRIBUTES. The main role of Angular 7 is to COMBINE the templates which ultimately CONTROL the DYNAMIC view that is visible to the USERS in the browsers.

UrlSegment is a modified feature of Angular 7 which is USED to add a new interface. In other words, UrlSegment Interface feature represents URL segment, constructor, properties and methods which are present in UrlSegment CLASS. MOREOVER, UrlSegement is one of the parts of URL, as it contains metric and PATH parameters which are associated and INTERLINKED with the segment.

Steps to update Angular 6 to Angular 7 are

• Remove deprecated FEATURES and components of RxJS 6 with the help of auto-update RULES from rxjs-tslint.
• Install the tool by using command npm install –g rxjs-tslin
• From the root of your project RUN rxjs-5-to 6-migrate –p scr/tsconfig.app.json
• remove rxjs-compat LIBRARY from rxjs-5-to 6-migrate –p scr/tsconfig.app.json
• Run command ng update @angular/[email protected]/core

Your Angular version gets updated to V7

Angular 7 has new and advanced level features such as

• Modernized v7.0.2 CLI prompts
• Reflect- METADATA poly-fill part for application performance
• Angular material and CDK ( COMPONENT Dev Kit)
• VIRTUAL scrolling PACKAGE
• Drag and Drop <@angular/cdk/drag-drop>
• Angular COMPATIBILITY compiler (ngcc)
• angular Do-bootstrap
• improved error handling
• dependency updates etc

In addition to all these features, Angular 7 also provides Documentation updates which include Angular console, @angular/Fire, NativeScript, StackBlitz, and Bazel, platform- browser, etc.

The main difference between Angular 7 and Angular 6 is -

An API stands for Application PROGRAMMING Interface. It is BASICALLY a SET of rules and tools for building software applications. In AngularJS, the Global API is a combination of global functions WRITTEN in Javascript which are used for tasks like comparing/iterating objects or CONVERTING data.

The COMMAND, NG generate service [service name] generates a service in Angular.

Here are the reasons to USE an AOT compiler in Angular:

• Faster rendering: Using the AOT compiler, browsers can download a pre-compiled version of the application. This ensures that the browser can render the application immediately using executable CODE without having to wait for the whole compilation.
• Less asynchronous requests: Using inline external HTML templates and CSS style sheets within the application, the compiler ELIMINATES separate ajax requests for those specific resource files.
• Reduced Angular framework download size: There's no need to download the Angular compiler if the app is already compiled. This is very advantageous and efficient as the compiler is almost half the size of Angular, so, not having to add that increases the application payload dramatically.
• Optimized Error Handling: Detecting EXISTING template ERRORS and reporting template binding errors during the building step before users can see.
• Enhanced Security: Compilation of HTML templates and other components into JS files before client-side rendering. This reduces the scope for risky JS evaluation or injection attacks. The AOT compiler the HTML templates and other components into JS files before they are served to the client. With no templates to read and no risky client-side JavaScript or HTML evaluation, there are fewer opportunities for injection attacks.

In Angular, during each navigation route, the Router sends navigation events through the Router Events property.

Here is the LIST of events range from when the navigation STARTS and ends too MANY points in between.

• NavigationStart
• RouteConfigLoadEnd
• GuardsCheckStart
• ActivationStart
• GuardsCheckEnd
• ResolveStart
• ActivationEnd
• NavigationEnd

export class AppComponent {
   constructor(private router: Router) {
   }
   ngOnInit() {
      this.router.events
      .PIPE(filter(event => event instanceof NavigationEnd))
      .subscribe(() => {
         ...
       });
   }
}

The Router.navigate is USED to specify a root URL through relative navigation. Here’s a function USING the above to navigate through DIFFERENT ARTICLES in Angular:

gotoDetails(articleId: any) {
   this.router.navigate(['/blog/', blogId]);
}

The utility functions PROVIDED by ANGULAR are:

• map() : Used to map values of different data types
• filter() : Used for filtering streams
• concat() : Used to concatenate multiple strings
• merge(): Used to recursively DESCEND into object properties in the SOURCE copy, while forming a deep copy of the same.

In Angular, the main.ts is the entry point of the application, which runs first when you RENDER a page in Angular. It compiles the application with JIT and bootstraps the Angular application. In Angular 2, you can BOOTSTRAP multiple environments to import a module SPECIFIC to the environment during which angular looks for a specific module to run first.

ECMAScript is a standard of CODING, implemented by JAVASCRIPT. In some browsers, Javascript implements Ecmascript 2015 STANDARDS(also called ES6). It is basically the JavaScript that browsers understand.

In Angular, the package.json file lets you keep a track of dependencies within a PROJECT. By using the reference of these packages in the dependency section, it enables you to USE a module BUNDLER such as webpack, browserify, etc. The package.json also helps you to keep your project linked to the specific versions of each package if the new version introduces any CHANGES.

When you have to pass the value from a parent component in ANgular to a child component, we have to use the property binding meaning that by doing so we are sending the value using the ATTRIBUTE on a component and thereby GET the parent using the @Input annotation for the example of property binding LIKE the below example: <my-child [myProp]="prop" />

Caching of Child’s Event/Method using the parent component.

This is used when we have to fire some event on click or maybe something else from the child component while passing it to the Parent.

<my-child [myProp]="prop" (onPropChange)="onPropChange($event)"</strong> /> Here, we have user onPropChange as event binding to CATCH and fire an event using EventEmitter.

The injectable DECORATOR in Angular 2 allows the functionality of the creation of a SERVICE to be injected and used in AngularJS modules by defining it as a PROVIDER in the Component Decorator.

Following is a SYNTAX to successfully create a service using the Injectable() decorator

import { Injectable } from '@angular/core';
import { ITEM } from './item';
import { ITEMS } from './mock-items';
@Injectable()
export class ItemService {
   selectedItems: Item[] = [];
   getItems(): Item[] {
   return ITEMS;
}
getSelectedItems(): Item[] {
   return this.selectedItems;
}
addItem(id:number): void {
   let item = ITEMS.find(ob => ob.id === id);
   if (this.selectedItems.indexOf(item) < 0) {
      this.selectedItems.push(item);
   }
}
removeItem(id:number): void {
   let item = this.selectedItems.find(ob => ob.id === id);
   let itemIndex = this.selectedItems.indexOf(item);
   this.selectedItems.splice(itemIndex, 1);
}

Modal footer is BASICALLY used when the template is fully loaded. User NEEDS to write the CODE inside the ngAfterViewInit then users will not get the footer element. Thus, footer modal is life cycle EVENT which is used to CHECK whether the Dom is fully loaded or not.

With application users being across the globe nowadays, Internationalization in Angular is used to SIMPLIFY the PROCESS of DESIGNING and preparing your APP for multiple languages.

The subscribe() function is observable in Angular 2 which defines how to OBTAIN or generate values or messages to be published. To execute a particular observable in a timely fashion, you will have to create NOTIFICATIONS using the subscribe() method.

An entry component in Angular is one that loads imperatively, i.e it can be loaded without any referenced in the template, by any type or CATEGORY. One can specify an entry component by either BOOTSTRAPPING it as a NgModule or even in a routing definition.

The <BASE href="/"> in Angular 2 is to direct the Angular Router to the STATIC PART of a URL. It helps the router to differentiate and make MODIFICATIONS to the URL accordingly.

In Angular 2, Bundling is KNOWN as the process of joining/combining multiple files into ONE single FILE. Third Party-libraries and other dependencies are generally bundled into a module for INCREASING productivity of code.

An IDE’s MAIN purpose is to provide a friendly CODING environment. Angular 2 SUPPORTS the following code-editors which are highly efficient:

• VISUAL STUDIO Code
• Sublime Text
• Atom Editor
• Webstorm
• Angular IDE
• ALM IDE
• Brackets
• Vim Editor

They are additionally called lambda features in different languages. Using fats arrow (=&GT;) we drop the want to use the 'function' keyword. Parameters are HANDED in the angular brackets &LT;>, and the characteristic expression is enclosed inside the CURLY brackets {}.

items.forEach((a) => {
    console.log(a);
    incrementedItems.push(a+1);
});

It is a famous LIBRARY that helps you add AID for contact gestures (e.g. rotate, swipe, pan, zoom ) to your page. We will enhance a swipe-able card. Angular 2 presents a TOKEN known as HAMMER_GESTURE_CONFIG which ACCEPTS a HammerGestureConfig type.

npm install hammerjs --save

Gulp is a MISSION runner that APPROVES you to DEFINE a sequence of repeatable tasks that can be run any time you need. You can automate boring matters like the minification and uglification of your javascript or some THING else you do in order to make your CODE production-ready.

The applications in angular 2 have an error handling option which also includes the react JS library to use the catch function. In TURN, the catch function includes a link that sends information about the error handler function. under this function one can send the error as a QUESTION to console file other INSTANCES will send it back in the main program to ensure the CONTINUATION of the OPERATION of the main program. Once it is fixed whenever the error arises it will be redirected in the browser's console.

USING the angular ROUTING command it GETS easier to navigate through the view page or any other file during any tasks. One can also configure the URL to redirect any other URL and this feature can also be handled to address the PROBLEM of "404 not found". By using the location services one can go back and forward along with the page history. Its syntax is- e can USE {path: '/OUR_PATH', redirectTo: ['redirectPathName']}

This is one of the most common Angular 2 interview questions.

Codelyzer refers to an open-source tool that is used to run or detect if the predefined coding guidelines are followed or not. It only performs the static code analysis in angular 2 and typescript project because all platforms FOLLOW a SET of easy and conventional coding to maintain it in a better way. Codelyzer also runs on the TOP of tslint where its coding convention is completely DEFINED in the tslint.json file. The DEVELOPER can also run it through an angular click.

Activatedroutesnapshot in Angular 2 is basically an immutable object which is used to represent a particular version of ActiveRoute.

For the IMPLEMENTATION of Activatedroutesnapshot object FOLLOWING SYNTAX can be used.

export CLASS ActivatedRoute {
   /** The current snapshot of this route **/
   snapshot: ActivatedRouteSnapshot;
}

Router state represents all the state of the router as a tree of activated routes.

interface RouterState extends Tree {
   snapshot: RouterStateSnapshot
   toString(): string
}

In actual, resolver (class) is a powerful technique which is USED to achieve the BEST USER experience when browsing between pages in the APPLICATION. For the implementation of the resolver class, it is important to create a new folder called resolves. Thereafter PUT resolvers with same template resolveName.resolver.ts

Here is the list of main BUILDING BLOCKS of ANGULAR 2:

• Modules
• Dependency injection
• Data binding
• Components
• Templates
• Directives
• Metadata
• Services

Services allow greater separation of CONCERNS in ANGULAR applications. They also provide MODULARITY by allowing developers to extract common functionalities out of components. Adding Services to Angular applications makes components FREE from data access code.

Service has the following features:

• Singleton, i.e. only one instance of service will exist throughout the application.
• Capable of returning data in the form of Observables and promises.
• Decorated with @Injectable() DECORATOR

Decorators allow developers to configure classes as elements by putting metadata on them.

The most COMMON decorators are @Component one for components and @INJECTABLE one for classes.

Decorators are new in TYPESCRIPT, and were not AVAILABLE in AngularJS. Angular2 ONWARDS offers four types of decorators and each plays a unique role - Class, Property, Method, and Parameter.

• AVOID INJECTING dynamic Html content
• Sanitize external HTML
• Do not PUT external URLs in the application
• Use AOT compilation
• Prevent XSRF attack by RESTRICTING API

This below MENTIONED will be the LIFECYCLE HOOKS ORDER in AngularJS.

• ngOnChanges()
• NGONINIT()
• ngDoCheck()
• ngAfterContentInit()
• ngAfterContentChecked()
• ngAfterViewInit()
• ngAfterViewChecked()
• ngOnDestroy()

In GENERAL, two-way data BINDING in ANGULAR 2 is the AUTOMATIC synchronization of data between the view components and model. Two-way data binding allows the users to treat the model as a single SOURCE of truth in your application.

An observable is an array where data arrives asynchronously.

Observables can help DEVELOPERS manage ASYNCHRONOUS data and are used within Angular, including event SYSTEM and HTTP client service. Angular uses REACTIVE Extensions (RxJS), a third-party library, to use Observables.

rootScope

It's an AngularJS SERVICE that implements the underlying EVENT and state management mechanism for AngularJS ATTRIBUTES, DIRECTIVES, views and controllers.

Whereas, it's a conventional parameter name given to a directive's link function's first ARGUMENT.

In Angular 2, a MODULE groups the various components, pipes, directives, and services in a WAY that assists them in combining with other MODULES for creating an application.

A module can be USED to hide or export pipes, directives, components and services.

Promises in Angular 2 execute asynchronous functions in SERIAL ORDER by registering promise OBJECT. Additionally, promises are PROVIDED by build-in $q service. Promises have generated a new way into native JavaScript as a part of the ES6 SPECIFICATION

It is an open source TOOL for running and CHECKING if the pre-defined CODING GUIDELINES were followed or not. It does static code analysis for typescript and angular projects.

It runs on top of tslint and coding conventions are defined in tslint.json file. Editors such as Visual Studio Code SUPPORT codelyzer by doing basic settings.

Using angular routing you can NAVIGATE from one view or page to another while performing your tasks. You can configure a URL to redirect to the next URL. This feature can be handled to ADDRESS the "404 Not FOUND" problem. Using location services in Angular routing you can go back and forward through the history of pages.

Syntax : We can use {PATH: '/OUR_PATH', redirectTo: ['redirectPathName']}

{path: '/404', NAME: 'PageNotFound', component: NotFoundComponent}