Typescript-201

Question 1

How can we define optional arguments?

Answer 1

function

Question 2

What are pipes used for?

Answer 2

Pipe asre used to format the data from src and bing them to the directive

Question 3

Which design principle does Service resembles?

Answer 3

SRP Single Repsoncibility Principle

Question 4

What is system js used for?

Answer 4

As a config & module loader

Question 5

What is app.component.ts

Answer 5

It is a standard way of specifying the bootstrapping class.

Question 6

What is @Component?

Answer 6

It is imported from @angular/core and it is used to bootstrap the class in app.component.ts

Question 7

What is the syntax and way of using @Component?

Answer 7

First import the component from @angular/core

While importing need not to use @ sign as @ mostly specifies that at the notation & aLso if you want to make a class that could be used else where for @

import {component} from ‘@angular/core’

// The @Component takes an object in parenthesis to //invoke
@Component({ // the below are must defined keys of //@Component
  selector : ápp',
  template : 'html code or path to html file'

})

export class AppComponent{ } // Make it available

Question 8

What is RxJS

Answer 8

Reactive Extension for JS

Question 9

What is RxJS used for?

Answer 9

Its a programming with emitting data, sync or async

Question 10

What is observable in RxJS?

Answer 10

Any emitting data from any src(array, api, object) is Observable

Question 11

Does Observable automatically notifies the observer?

Answer 11

Yes the Observable notifies the observer when data starts emitting or arrive

Question 12

What is the difference between Observable & Promise?

Answer 12

The promise gets the data one time, and you need to invoke the method again, with observable it will emit multiple times

Question 13

Can you write a simple Observable code?

Answer 13

var obs = Rx.Observale.of(10);
obs.subscribe(function(d){
    console.log(d); // prints 10
 });

Question 14

Does Observable has the capability to invoke the error or success block? Say with E.g.

Answer 14

Yes

var obs = Rx.Observable.of(10);
obs.subscribe(
    function(d){
 d=   d+d;
}, function(e){

console.log(ërror’’);
}, function(){
console.log(“success”);
}

);

so all three goes into the paren and as args, the success case wont have any args

Question 15

What does from operator does?

Answer 15

It helps convert array into Observable

Question 16

Can you write one e.g for creating an observer on settimeout ?

Answer 16

So Observable is a sort of wrapper around any function. The Observable will be there to act when the data is knocked. So

var timeout : Observable = Observable.create(
(observer: Observer(string)) => {
setTimeout(() // this shows the function itself will be //executed
=> // this shows the projection or giving from one to //another
{
observer.next(“kiran”); // so you omit on observer
}, 2000);

}

)

timeout. subscribe((v) => {
this. name = v;

});

Question 17

How do specify the return type or a var type?

Answer 17

export let users : User[] = [{name : “prc””}] ;

so declare : define = assign

Question 18

How can you create a model object?

Answer 18

export class Model exteds/implements class/interface {

}

Question 19

What does the get of http returns?

Answer 19

It returns an Observable object with Response type

Question 20

What is included in the Response object?

Answer 20

basic, CORS, default response headers, method to get the response data as text and as JSON, with other props regarding http response received from the request

Question 21

Where does the response object of http passed to?

Answer 21

The response object is passed to the callback function attached to the subscribe object

Question 22

Specify one e.g. of get, put and post of http ?

Answer 22

Yes

public get(book : Book) : Observable = function(){
this.http.get(this.url);
this.post(this.url, JSON.stringify(book));
this.http.put(this.url/ ‘${book.id}’, JSON.stringify(book));
}

Question 23

Can we have two directives in one tag

Answer 23

No

Question 24

What is window.location.href?

Answer 24

It will give the current domain

Question 25

Can we access JS Global vars in interpolation tag

Answer 25

Nope

Question 26

What is window.location.href?

Answer 26

It will give the current domain

Question 27

Can we access JS Global vars in interpolation tag

Answer 27

Nope

Question 28

How can we do attribute and property binding?

Answer 28

using [] ,

Question 29

How to generate components in TS?

Answer 29

ng generate [component, module, service], generationg component will auto add into the module