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angularHooks.txt
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angularHooks.txt
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https://github.com/CodAffection/Angular-7-Master-Detail-CRUD-with-Web-
API/tree/master/Angular7/src
https://mindmajix.com/javascript-interview-questions
https://medium.com/coderbyte/a-tricky-javascript-interview-question-asked-by-
google-and-amazon-48d212890r7/srcsrc
https://angulardemoshopee.firebaseio.com/
//cli: command line interface
//npm: node package manager
Begin with angular:
install Node Js & then npm(install npm)
In a folder run command : npm install -g @angular/cli
For crate new project : ng new my-app
To run app: ng serve or ng serve --open or npm start
Install Emmit.
The Angular CLI is a command line interface tool that can create a project, add
files, and perform a variety of ongoing development tasks such as testing,
bundling, and deployment.
----------------------------------------------------------------
@Component() : Decorator
Creating component:
Command : ng generate component <component-name> / ng g c <component-name>
// ng g c <component-name> .spec false
import { Component } from '@angular/core';
@Component({
selector: 'app-root',
//property : [app-root] //class : [.app-root]
templateUrl: './app.component.html',//html : '<p> component </p>'
styleUrls: ['./app.component.css']
// style: '[.pop {color:#f00;}]'
})
export class AppComponent {
title = 'app';
constructor(){
}
}
----------------------------------------------------------------
Data binding:
Interpolation: {{ <variable> or '<string>' }}
Proper two-way binding : [()]
() : sending to component
[] : receving from component
Binding Class : [ngClass] = "{}"
<p [ngClass]="{bg-black: this.pop == 'online'}"> </p>
<div [ngClass]="['example-class', 'other-class']"></div>
<div [class.example-class]="condition"></div>
<div [className]="'class' + someValue"></div>
<div [ngClass]="{
'example-class': condition,
'other-class': !condition
}">
</div>
Here we add condition, if its true than it will add bg-black.
Binding Style : [ngStyle] = "{}"
<p [ngStyle]="{backgroungColor: this.pop == 'online' ? 'red' : 'blue';}">
Binding events : (<event>): "<fun-name>() or any-code"
<p (click)="getInfo()"></p> or <p (click)="this.pop = !this.pop"></p>
Binding if : *ngIf="any boolean value"
<p *ngIf="visible; else noVisible">show default</p>
<ng-template #noVisible> <p> Show else </p></ng-template>
Binding switch :
<ul [ngSwitch]="<property>">
<li *ngSwitchCase = "value"> </li>
</ul>
Binding for : *ngFor="let item of list; let i = index"
<ul>
<li *ngFor="let item of itemlList; let i = index"> <span> {{ i }}
{{item}}</span>
</li>
</ul>
:host-context:
:host-context(.red-theme) .btn-theme {
background: red;
}
<div class="blue-theme">
<themeable-button></themeable-button>
</div>
:host : root element e.g <themeable-button></themeable-button>
::ng-deep : :host ::ng-deep or /deep/ or >>>
----------------------------------------------------------------
Lifecycle hook
ngOnChanges: this executed multiple time, this is executed right at start when new
component is created , it is always called one of inline bound property changes,
that means these proprties receive new values.
ngOnInit : get executed once the component as initialized, it can also run after
constructor is called
ngDoCheck: it runs multiple time, this run whenever change detection runs, its runs
when some thing chage is happend in template, on ever check angular makes, but not
such if any thing but also when we click on button because its an event angulr as
to check is some thing as changed or time fired or observable fired, its good if
you need some check on every chagne detection cycle like.
ngAfterContentInit: is called when ever the content which is project to the Y
ngcontent has been initialized , not the view of the content itself but instead you
could say the view of the parent tell what component esspecially apart which will
get added to our component through ngcontent
ngAfterContentChecked: is executed whenevr change detection checked this content
we're projecting into our component
ngAfterViewInit: is called when ever view of our oen component as been finised
inilizing
ngAfterViewChecked: all the changes has been checked and displayed on our view or
no change is detected by angular
ngdestory: when component is destoryed
----------------------------------------------------------------
Sending data from one component to another:
Sending from child to parent:
parent
Html :
<div> <app-child (callParentEvent)="parentCalled()"> </app-child> </div>
Controller:
export class parent {
parentCalled(){}
}
child
Html :
<button (click)="fireEvent($event)">Click</button>
Controller:
import { OutPut, EventEmmiter } from '@angular/core';
export class parent {
@Output() callParentEvent = new EventEmmiter<{name:string}>();
fireEvent(event){
this.callParentEvent.emit({name:this.name});
}
}
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Sending from parent to child
parent
Html :
<div> <app-child [parData]="name"> </app-child> </div>
Controller:
export class parent {
name = "popups";
parentCalled(){}
}
child
Html :
<button (click)="fireEvent($event)">Click</button>
Controller:
import { Input } from '@angular/core';
export class parent {
@Input() parData:string;
fireEvent(event){
console.log(this.parData);
}
}
--------------------------------------------------------------------
Remove encapsulation
@Component({
selector: 'app-server-element',
templateUrl: './server-element.component.html',
styleUrls: ['./server-element.component.css'],
encapsulation: ViewEncapsulation.Emulated //.Native//.None
})
---------------------------------------------------------------------
Reference Child refernce element :
template : <h1 #heading> Heading </h1>
Controler : @ViewChild('heading') headRef: ElementRef;
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Refering child in ng-control:
Parent :
<div>
<app-child>
<p #childPanel> child element</p>
</app-child>
</div>
child
<div class="panel-body">
<ng-content> </ng-content>
</div>
Child component:
@ContentChild('childPanel') contChild: ElementRef;
------------------------------------------------------------------------
Directive
Creating Directive:
import { Directive } from '@angular/core';
@Directive({
selector:"[appHighLight]"
})
export class HighLight{
@Input('appHighLight') highlightColor:string = 'blue';
@HostBinding('style.backgroundColor') backgroundColor: string;
constructor(private elRef:ElementRef, private render: Renderer2) {
}
ngOnInit(){
this.backgroundColor = this.defaultColor;
// this.render.setStyle(this.elRef.nativeElement, 'background-
color', 'blue');
}
@HostListener('mouseenter') mouseover(eventData: Event){
// this.render.setStyle(this.elRef.nativeElement, 'background-color',
'blue');
this.backgroundColor = this.highlightColor;
}
@HostListener('mouseleave') mouseleave(eventData: Event){
// this.render.setStyle(this.elRef.nativeElement, 'background-color',
'transparent');
this.backgroundColor = this.defaultColor;
}
}
html : <p [appHighLight]="'red'" defaultColor="yellow"> Better directive</p>
Add created directive reference in Module declarations
declarations: [
AppComponent,
appHighLight],
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Changing Property of element that has directive
constructor(private elementRef:ElementRef) {
elementRef.nativeElement.style.backgroundColor = 'red';
}
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Creating structural directive
html: <div *appUnless="onlyOdd">
<p appBasicHighLight>Only odd</p>
</div>
Directive :
@Directive({
selector: '[appUnless]'
})
export class UnlessDirective {
@Input() set appUnless(condition:boolean){
if(!condition){
this.vcRef.createEmbeddedView(this.templateRef);
}
else
{
this.vcRef.clear();
}
}
constructor(private templateRef: TemplateRef<any>, private vcRef:
ViewContainerRef) {
}
}
--------------------------------------------------------------------------------
Creating services: that can be used all over the project
export class service1{
}
Using service:
add service in Module provider:
@NgModule({
provider:[service1]
})
or
/---------------------------\
@Injectable({
providedIn: 'root'
})
\---------------------------/
we can also add in component
in Component
export class NewAccountComponent {
constructor(private loggingService:service1){
}
}
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
For using service in service use
@Injectable() above class name
import { LoggingService } from './logging.service';
@Injectable()
export class AccountsService {
constructor (private loggingService: LoggingService){
}
}
-----------------------------------------------------------------------------------
Routing:
Setting Router settings In app module:
import { Routes, RouterModule } from @angular/router;
const appRoutes: Routes [
{path:"",component: HomeComponent}, //default route
{path:"users",component: UserComponent},//users component
route
{path:"users/login",component: LoginComponent}//login
component under users component route
{path:"users/:id/:name",component: UserDetailComponent}, //
this would open users coponent with taking user id & name in url and accepting that
in component
{path:"customer",component: CustomerComponent, children:[
{path:":id",component:CustInfoComponent}
]},//adding child routes
];
@NgModule({
imports:[RouteModule.forRoot(appRoutes)],
export: RouteModule
})
export class AppRoutingModule {
}
In app.module.ts
@NgModule({
declaration:[<all components & Drivers>],
providers:[<services>],
imports:[<all modules>, AppRoutingModule],
bootstarp:[AppComponent]
})
export class AppModule { }
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Loading module main module of pages
const routes: Routes = [
{
path: 'login'
loadChildren: './login/login.module#LoginModule'
}
]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
To load routed component
<router-outlet></router-outlet>
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Route to link in html
<a routerLink="/users">//(o/p: /users/)
multiple options
<a [routerLink]=["/users","1","edit"]> //(o/p: /users/1/edit)
from code:
export class HomeComponent{
constructor(private router: Router){
}
onBtnClick(){
this.router.navigate(['/server','1','edit'], {queryParams:
{allowEdit:1}, fragment:'loading'});//(o/p: /server/1/edit?allowEdit=1#loading)
//this.routes.navigate(['servers'],{relativeTo:this.routeActive});//
relative link
}
}
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
adding class active to activated route link
<li role="presentation" routerLinkActive="active"
[routerLinkActiveOptions]="{exact:true}"><a routerLink="/">Home</a></li>
routerLinkActive: which class need to added
routerLinkActiveOptions: to activate current active link
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
To get current activated link
export class users{
private id:number;
constructor(private routerActive: ActivatedRoute){
this.id=this.routerActive.spanshot.params['id'];
//observable to update async
this.routerActive.params.subscribe(
(params: Params)=>{
this.id = params.id;
}
);
}
}
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
for preserving query parameters
this.routes.navigate(['edit'],{relativeTo: this.routeActive,
queryParamsHandling:'preserve'});
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
CanDeactivate:
This would help while moving out of form when some change are that should not be
lost
1)Create a gaurd : can-deactiveate-guard.service.ts
import { CanDeactivate } from @angular/router;
export Interface CanComponentDeactivate {
CanDeactivate()=>Observable<boolean> | Promise<boolean> | boolean;
}
export class CanDeactivateGaurd implements
CanDeactivate<CanComponentDeactivate> {
CanDeactivate(component: CanDeactivateGaurd,
currentRoute:ActivateRouteSnapshot,
currentState: RouterStateSnapshot,
nextState: RouterStateSnapshot):Observable<boolean> |
Promise<boolean> | boolean{
return component.canDeactivate();
}
In component:
import above service in component
import { CanComponentDeactivate } from './can-deactiveate-guard.service';
Add below function in component: if this returns false component will not move to
other link
canDeactivate(): Observable<boolean> | Promise<boolean> | boolean {
if(!this.allowEdit){
return true;
}
if((this.serverName !== this.server.name || this.serverStatus !==
this.server.status) && !this.changesProperty)
{
return confirm("Do you want discard changes?");
}
else {
return true;
}
}
}
In route add canDeactivate
{path: ':id/edit', component:EditServerComponent, canDeactivate:
[CanDeactivateGuard]},
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Auth
Create service
export class AuthGaurd implements CanActivate, CanActivateChild {
constructor(private authService: AuthService, private router: Router){
}
//can activate should return true or false
canActivate(route: ActivatedRouteSnapshot,
state: RouterStateSnapshot): Observable<boolean> | Promise<boolean> |
boolean {
return this.authService.isAuthentication().then(
(authentication: boolean)=>{
if(authentication){
return true;
}
else {
this.router.navigate(['/']);
}
}
)
}
canActivateChild(route: ActivatedRouteSnapshot,
state: RouterStateSnapshot): Observable<boolean> | Promise<boolean> |
boolean {
return this.canActivate(route,state);
}
}
In route : add AuthGaurd
{path: 'servers',
//canActivate:[AuthGaurd],
canActivateChild:[AuthGaurd],
component:ServersComponent, children:[
{path: ':id/edit', component:EditServerComponent, canDeactivate:
[CanDeactivateGuard]},
{path: ':id', component:ServerComponent, resolve:{server:ServerResolver}}
]},
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Resolver
To send resolved data in Data.
Create Resolver :
interface Server {
id:number;
name:string;
status:string;
}
@Injectable()
export class ServerResolver implements Resolve<Server> {
constructor(private serverService: ServersService){
}
resolve(route: ActivatedRouteSnapshot, state:
RouterStateSnapshot):Observable<Server> | Promise<Server> | Server{
return this.serverService.getServer(+route.params['id']);
}
}
To access data in component
import { Data } from '@angular/router';
//data will have resolved data
//routeActive:ActivatedRoute
ngOnInit() {
this.routeActive.data.subscribe((data:Data)=>{
this.server = data['server'];
});
}
Route :
{path: ':id', component:ServerComponent, resolve:{server:ServerResolver}}
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Not found page:
{path: 'not-found', component:ErrorPageComponent, data:{message: 'Page not
found'}},
{path: '**', redirectTo:'/not-found'},
--------------------------------------------------------------------------------
RxJs
1)subject
import { Subject } from 'rxjs/Subject';
//in service
export class UserService {
serviceSub = new Subject<Ingredient[]>();
provideFunction(){
this.serviceSub.next(<return array>);
}
}
how to use
import { Subscription } from 'rxjs/Subscription';//Import
private subscription: Subscription;
// to store subscription
this.subscription = this.shoppingListService.ingredientChange.subscribe
((ingredients:Ingredient[])=> {this.ingredients = ingredients});
// to execute
subscription
2)interval
import { observable } from 'rxjs/observable';
import 'rxjs/Rx';
let number = observable.interval(1000);
number.subscribe((num:number)=>{
setTimeInterval(()=>{
console.log(num);
},1000)
},
(error)=>{}
(complete)=>{}
)
this will print in console
1
2
3
.
.
... ever 1 second
3) Creating own observable
let obser = observable.create((observer:Observer)={
setTimeout(()=>{
observer.next("hello 1");
},2000);
setTimeout(()=>{
observer.next("hello 2");
},4000);
});
obser.subscribe((str:string)=>{
console.log(str);
},
(error)=>{},
(complete)=>{}
);
----------------------------------------------------------------------------------
Form :
1) Template
2) Reactive
1) Template: defining model (ngModel) in template
In app.module.ts
import { FormsModule } from '@angular/forms';
@NgModel({
import :[FormsModule]
})
Note : [] add property value from class to template// [ngModel]
() set value from template to class //(click)
[()] two way binding //[(ngModel)] = "username"
For submitting form: (ngSubmit)="<function_name>(<arg list>)"
i) add ngModel in input control: also add name to control
<input
type="text"
id="username"
class="form-control"
ngModel
name="username"
required #username="ngModel">
//#username="ngModel" : add refernce to model
ii) FromGroup:
ngModelGroup="userGroupData"
#userGroupData="ngModelGroup"
e.g:<div
id="user-data"
ngModelGroup="userGroupData"
#userGroupData="ngModelGroup"></div>
iii) Adding value to control: [value]="gender"
<input
type="radio"
name="gender"
ngModel
[value]="gender"
required>
iv) Validation: username is reference of control (#username)
!username.valid : if value is not valid
username.touched: if control is not touched than : false
emai : add email in input control for valiadting email.
[disabled]: for disabling input
required: for setting required input
v) Submiting form: (ngSubmit)
<form (ngSubmit)="onSubmit(f)" #f="ngForm">
// here 'f' as argument in onSubmit is from elementRef
vi) For storing form control: @ViewChild('f') form:NgForm;
vii) For setting values for all form control:
@ViewChild('f') form:NgForm;
this.form.setValue({
userGroupData:{
username:'Sarvan',
email:'sarvan@gmail.com'
},
quesionAnswer:"",
secret : 'pet',
gender: 'male'
});
or
for signle value:
this.form.form.patchValue({
userGroupData:{
username:'Sarvan'
}
});
viii) Reseting form : this.form.reset(); //look for vi point
ix) Getting values for form control:
// here this.user is object declare in class
this.user.email = this.form.value.userGroupData.email;
//its in
grp userFroupData this.user.secretQuestion =
this.form.value.secretQuestion;
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
2) Reactive: Control are added in templates but assigned there ref in class
In app.module.ts // remove FormsModule
import { ReactiveFormsModule } from '@angular/forms';
@NgModel({
import :[ReactiveFormsModule]
})
````````i) Creating form group: signupForm:FormGroup;
This is required for storing form conrtol as a group of input/form
controls
Also need to specify form group in template:
<form [formGroup]="signupForm" (ngSubmit)="onSubmit()">
<div formGroupName="userData">
and
setting control: formControlName="username"
<input
type="text"
id="username"
formControlName="username"
class="form-control">
````````ii) Creating control:
FormControl(<defaultValue>, <validation>, <Async Validation>)
validation is function reference, similar asyn
e.g
this.signupForm = new FormGroup({
'userData': new FormGroup({
'username': new FormControl(null,
[Validators.required, this.forbinddenNames.bind(this)]),
'email': new FormControl(null,
[Validators.required, Validators.email], this.asyncForbinddenValidate)
}),
'gender': new FormControl('male'),
'hobbies': new FormArray([])
});
````````iii)setting value to control is similar as template
//For getting form control use <formObject>.get('<controlName/path>')
````````iv) resetting :
//Resetting all form control
this.signupForm.reset();
//Resetting single control
this.signupForm.get('userData.username').reset();// here userData is
formgroup(formGroupName) & username is control.
````````v) Value change trigger observalble: valueChanges
this.signupForm.valueChanges.subscribe((value)=>{
console.log(value);
});
````````vi) Status change trigger observalble: statusChanges
this.signupForm.statusChanges.subscribe((state)=>{
console.log(state);
});
````````vii) Creating custome validation function:
forbinddenNames(control:FormControl):{[s:string]:boolean}{
if(this.forbinddenusername.indexOf(control.value) !== -1){
return {'nameIsForbidden':true};
}
return null;
}
How to use in template:
'username': new FormControl(null, [Validators.required, this.forbinddenNames.bind
(this)]),
Showing error message: signupForm.get('userData.username')
<span
*ngIf="!signupForm.get('userData.username').valid && signupForm.get
('userData.username').touched"
class="help-bolck">
<span *ngIf="signupForm.get('userData.username').errors
['nameIsForbidden']">Invalid user name.</span>
<span *ngIf="signupForm.get('userData.username').errors
['required']">Please enter user name.</span>
</span>
`````````viii) Async validation function:
asyncForbinddenValidate(control:FormControl):Promise<any> | Observable<any> {
const promise = new Promise<any>((resolve, reject)=>{
setTimeout(() => {
if(control.value == 'test@test.com'){
resolve({'emailIsForbidden':true});
}
else {
resolve(null);
}
}, 1500);
})
return promise;
}
How to use :
'email': new FormControl(null, [Validators.required,
Validators.email], this.asyncForbinddenValidate)
In template error message:
<span *ngIf="signupForm.get('userData.username').errors
['nameIsForbidden']">Invalid user name.</span>