Q1. Name the building blocks of Angular.
The Angular application is made using the
following:
·
Modules
·
Component
·
Template
·
Directives
·
Data Binding
·
Services
·
Dependency Injection
·
Routing
Q2. What is View Encapsulation?
View Encapsulation decides
whether the styles defined in a component can affect the entire application or
not. There are three ways to do this in Angular:
Emulated: styles from other
HTML spread to the component.
Native: styles from other
HTML do not spread to the component.
None: styles defined in a
component are visible to all components.
Q3. What are Services in Angular and what command is used to create a
service?
Services help us in not
repeating the code. With the creation of services, we can use the same code
from different components. Here is the command to create a service in angular,
ng g service User (a UserService is created when this command is used).
Q4. Explain the usage of {{}}?
The set of brackets
{{}} when used with an HTML tag, represent data from a component. For example,
on a HTML page which has <h1>{{variableName}}</h1>, here the
‘variableName’ is actually typescript (component) data representing its value
on the template; i.e., HTML. This entire concept is called String
Interpolation.
Q5. How is SPA (Single Page Application) technology different from the
traditional web technology?
In traditional web
technology, the client requests for a web page (HTML/JSP/asp) and the server
sends the resource (or HTML page), and the client again requests for another
page and the server responds with another resource. The problem here is a lot
of time is consumed in the requesting/responding or due to a lot of reloading.
Whereas, in the SPA technology, we maintain only one page (index.HTML) even
though the URL keeps on changing.
Q6. Differentiate between Observables and Promises.
Observables are lazy, which
means nothing happens until a subscription is made. Whereas Promises are eager;
which means as soon as a promise is created, the execution takes place.
Observable is a stream in which passing of zero or more events is possible and
the callback is called for each event. Whereas, promise handles a single
event.
Q7. What is an AsyncPipe in Angular?
When an observable or promise
returns something, we use a temporary property to hold the content. Later, we
bind the same content to the template. With the usage of AsyncPipe, the promise
or observable can be directly used in a template and a temporary property is
not required.
Q8. Explain Authentication and Authorization.
Authentication: The user
login credentials are passed to an authenticate API (on the server). On the
server side validation of the credentials happens and a JSON Web Token (JWT) is
returned. JWT is a JSON object that has some information or attributes about
the current user. Once the JWT is given to the client, the client or the
user will be identified with that JWT.
Authorization: After
logging in successfully, the authenticated or genuine user does not have access
to everything. The user is not authorized to access someone else’s data,
he/she is authorized to access some data.
Q9. What is AOT Compilation?
Every angular application
gets compiled internally. The angular compiler takes javascript code, compiles
it and produces javascript code again. Ahead-of-Time Compilation does not
happen every time or for every user, as is the case with Just-In-Time (JIT)
Compilation.
Q10. What is Redux?
It is a library which helps
us maintain the state of the application. Redux is not required in applications
that are simple with the simple data flow, it is used in Single Page
Applications
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