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Angular.io Cheat Sheet

ANGULAR (2+) CHEATSHEET

NG MODULES

import { NgModule } from '@angular/core';

@NgModule({
  declarations: ...,
  imports: ...,
  exports: ...,
  providers: ...,
  bootstrap: ...
})

Defines a module that contains components, directives, pipes, and providers.

class MyModule {}

List of components, directives, and pipes that belong to this module.

declarations: [MyRedComponent, MyBlueComponent, MyDatePipe] 

List of modules to import into this module. Everything from the imported modules is available to declarations of this module.

imports: [BrowserModule, SomeOtherModule] 

List of components, directives, and pipes visible to modules that import this module.

exports: [MyRedComponent, MyDatePipe] 

List of dependency injection providers visible both to the contents of this module and to importers of this module.

providers: [MyService, { provide: ... }]  

List of components to bootstrap when this module is bootstrapped.

bootstrap: [MyAppComponent] 

TEMPLATE SYNTAX

Binds property value to the result of expression firstName.

<input [value]="firstName"> 

Binds attribute role to the result of expression myAriaRole.

<div [attr.role]="myAriaRole">  

Binds the presence of the CSS class extra-sparkle on the element to the truthiness of the expression isDelightful.

<div [class.extra-sparkle]="isDelightful">  

Binds style property width to the result of expression mySize in pixels. Units are optional.

<div [style.width.px]="mySize"> 

Calls method readRainbow when a click event is triggered on this button element (or its children) and passes in the event object.

<button (click)="readRainbow($event)">  

Binds a property to an interpolated string, for example, "Hello Seabiscuit". Equivalent to:

<div [title]="'Hello ' + ponyName">
<div title="Hello {{ponyName}}">  

Binds text content to an interpolated string, for example, "Hello Seabiscuit".

<p>Hello {{ponyName}}</p> 

Sets up two-way data binding. Equivalent to:

<my-cmp [title]="name" (titleChange)="name=$event">
<my-cmp [(title)]="name"> 

Creates a local variable movieplayer that provides access to the video element instance in data-binding and event-binding expressions in the current template.

<video #movieplayer ...>
<button (click)="movieplayer.play()">
</video>  

The * symbol turns the current element into an embedded template. Equivalent to:

<ng-template [myUnless]="myExpression"><p>...</p></ng-template>
<p *myUnless="myExpression">...</p> 

Transforms the current value of expression cardNumber via the pipe called myCardNumberFormatter.

<p>Card No.: {{cardNumber | myCardNumberFormatter}}</p> 

The safe navigation operator (?) means that the employer field is optional and if undefined, the rest of the expression should be ignored.

<p>Employer: {{employer?.companyName}}</p>  

An SVG snippet template needs an svg: prefix on its root element to disambiguate the SVG element from an HTML component.

<svg:rect x="0" y="0" width="100" height="100"/>  

An root element is detected as an SVG element automatically, without the prefix.

<svg>
  <rect x="0" y="0" width="100" height="100"/>
</svg>  

BUILT-IN DIRECTIVES

import { CommonModule } from '@angular/common';

Removes or recreates a portion of the DOM tree based on the showSection expression.

<section *ngIf="showSection"> 

Turns the li element and its contents into a template, and uses that to instantiate a view for each item in list.

<li *ngFor="let item of list">  

Conditionally swaps the contents of the div by selecting one of the embedded templates based on the current value of conditionExpression.

<div [ngSwitch]="conditionExpression">
  <ng-template [ngSwitchCase]="case1Exp">...</ng-template>
  <ng-template ngSwitchCase="case2LiteralString">...</ng-template>
  <ng-template ngSwitchDefault>...</ng-template>
</div>  

Binds the presence of CSS classes on the element to the truthiness of the associated map values. The right-hand expression should return {class-name: true/false} map.

<div [ngClass]="{'active': isActive, 'disabled': isDisabled}"> 

Allows you to assign styles to an HTML element using CSS. You can use CSS directly, as in the first example, or you can call a method from the component.

<div [ngStyle]="{'property': 'value'}">
<div [ngStyle]="dynamicStyles()"> 

FORMS

import { FormsModule } from '@angular/forms';

Provides two-way data-binding, parsing, and validation for form controls.

<input [(ngModel)]="userName">  

CLASS DECORATORS

import { Directive, ... } from '@angular/core';

Declares that a class is a component and provides metadata about the component.

@Component({...})
class MyComponent() {}  

Declares that a class is a directive and provides metadata about the directive.

@Directive({...})
class MyDirective() {}  

Declares that a class is a pipe and provides metadata about the pipe.

@Pipe({...})
class MyPipe() {} 

Declares that a class can be injected into the constructor of another class by the dependency injector.

@Injectable()
class MyService() {}  

DIRECTIVE CONFIGURATION

@Directive({ property1: value1, ... })

Specifies a CSS selector that identifies this directive within a template. Supported selectors include element, [attribute], .class, and :not().

selector: '.cool-button:not(a)' 

Does not support parent-child relationship selectors.

List of dependency injection providers for this directive and its children.

providers: [MyService, { provide: ... }]  

COMPONENT CONFIGURATION

@Component extends @Directive, so the @Directive configuration applies to components as well

If set, the templateUrl and styleUrl are resolved relative to the component.

moduleId: module.id 

List of dependency injection providers scoped to this component's view.

viewProviders: [MyService, { provide: ... }]  

Inline template or external template URL of the component's view.

template: 'Hello {{name}}'
templateUrl: 'my-component.html'  

List of inline CSS styles or external stylesheet URLs for styling the component’s view.

styles: ['.primary {color: red}']
styleUrls: ['my-component.css'] 

CLASS FIELD DECORATORS FOR DIRECTIVES AND COMPONENTS

import { Input, ... } from '@angular/core';

Declares an input property that you can update via property binding

<my-cmp [myProperty]="someExpression">
@Input() myProperty;  

Declares an output property that fires events that you can subscribe to with an event binding

<my-cmp (myEvent)="doSomething()">
@Output() myEvent = new EventEmitter(); 

Binds a host element property (here, the CSS class valid) to a directive/component property (isValid).

@HostBinding('class.valid') isValid;  

Subscribes to a host element event (click) with a directive/component method (onClick), optionally passing an argument ($event).

@HostListener('click', ['$event']) onClick(e) {...} 

Binds the first result of the component content query (myPredicate) to a property (myChildComponent) of the class.

@ContentChild`(myPredicate)` myChildComponent;  

Binds the results of the component content query (myPredicate) to a property (myChildComponents) of the class.

@ContentChildren`(myPredicate)` myChildComponents;  

Binds the first result of the component view query (myPredicate) to a property (myChildComponent) of the class. Not available for directives.

@ViewChild`(myPredicate)` myChildComponent; 

Binds the results of the component view query (myPredicate) to a property (myChildComponents) of the class. Not available for directives.

@ViewChildren`(myPredicate)` myChildComponents; 

DIRECTIVE AND COMPONENT CHANGE DETECTION AND LIFECYCLE HOOKS (implemented as class methods)

Called before any other lifecycle hook. Use it to inject dependencies, but avoid any serious work here.

constructor(myService: MyService, ...) { ... }  

Called after every change to input properties and before processing content or child views.

ngOnChanges(changeRecord) { ... } 

Called after the constructor, initializing input properties, and the first call to ngOnChanges.

ngOnInit() { ... }  

Called every time that the input properties of a component or a directive are checked. Use it to extend change detection by performing a custom check.

ngDoCheck() { ... } 

Called after ngOnInit when the component's or directive's content has been initialized.

ngAfterContentInit() { ... }  

Called after every check of the component's or directive's content.

ngAfterContentChecked() { ... } 

Called after ngAfterContentInit when the component's views and child views / the view that a directive is in has been initialized.

ngAfterViewInit() { ... } 

Called after every check of the component's views and child views / the view that a directive is in.

ngAfterViewChecked() { ... }  

Called once, before the instance is destroyed.

ngOnDestroy() { ... } 

DEPENDENCY INJECTION CONFIGURATION

Sets or overrides the provider for MyService to the MyMockService class.

{ provide: MyService, useClass: MyMockService } 

Sets or overrides the provider for MyService to the myFactory factory function.

{ provide: MyService, useFactory: myFactory } 

Sets or overrides the provider for MyValue to the value 41.

{ provide: MyValue, useValue: 41 }  

ROUTING AND NAVIGATION

import { Routes, RouterModule, ... } from '@angular/router';
const routes: Routes = [
  { path: '', component: HomeComponent },
  { path: 'path/:routeParam', component: MyComponent },
  { path: 'staticPath', component: ... },
  { path: '', component: ... },
  { path: 'oldPath', redirectTo: '/staticPath' },
  { path: ..., component: ..., data: { message: 'Custom' } }
]);

Configures routes for the application. Supports static, parameterized, redirect, and wildcard routes. Also supports custom route data and resolve.

const routing = RouterModule.forRoot(routes); 

Marks the location to load the component of the active route.

<router-outlet></router-outlet>
<router-outlet name="aux"></router-outlet>

Creates a link to a different view based on a route instruction consisting of a route path, required and optional parameters, query parameters, and a fragment. To navigate to a root route, use the / prefix; for a child route, use the ./prefix; for a sibling or parent, use the ../ prefix.

<a routerLink="/path">
<a [routerLink]="[ '/path', routeParam ]">
<a [routerLink]="[ '/path', { matrixParam: 'value' } ]">
<a [routerLink]="[ '/path' ]" [queryParams]="{ page: 1 }">
<a [routerLink]="[ '/path' ]" fragment="anchor">

The provided classes are added to the element when the routerLink becomes the current active route.

<a [routerLink]="[ '/path' ]" routerLinkActive="active">  
class CanActivateGuard implements CanActivate {
  canActivate(
    route: ActivatedRouteSnapshot,
    state: RouterStateSnapshot
  ): Observable<boolean>|Promise<boolean>|boolean { ... }
}

An interface for defining a class that the router should call first to determine if it should activate this component. Should return a boolean or an Observable/Promise that resolves to a boolean.

{
  path: ...,
  canActivate: [CanActivateGuard]
}  

class CanDeactivateGuard implements CanDeactivate<T> {
  canDeactivate(
    component: T,
    route: ActivatedRouteSnapshot,
    state: RouterStateSnapshot
  ): Observable<boolean>|Promise<boolean>|boolean { ... }
}

An interface for defining a class that the router should call first to determine if it should deactivate this component after a navigation. Should return a boolean or an Observable/Promise that resolves to a boolean.

{
  path: ...,
  canDeactivate: [CanDeactivateGuard]
}

class CanActivateChildGuard implements CanActivateChild {
  canActivateChild(
    route: ActivatedRouteSnapshot,
    state: RouterStateSnapshot
  ): Observable<boolean>|Promise<boolean>|boolean { ... }
}

An interface for defining a class that the router should call first to determine if it should activate the child route. Should return a boolean or an Observable/Promise that resolves to a boolean.

{
  path: ...,
  canActivateChild: [CanActivateGuard],
  children: ...
}

class ResolveGuard implements Resolve<T> {
  resolve(
    route: ActivatedRouteSnapshot,
    state: RouterStateSnapshot
  ): Observable<any>|Promise<any>|any { ... }
}

An interface for defining a class that the router should call first to resolve route data before rendering the route. Should return a value or an Observable/Promise that resolves to a value.

{
  path: ...,
  resolve: [ResolveGuard]
}

class CanLoadGuard implements CanLoad {
  canLoad(
    route: Route
  ): Observable<boolean>|Promise<boolean>|boolean { ... }
}

An interface for defining a class that the router should call first to check if the lazy loaded module should be loaded. Should return a boolean or an Observable/Promise that resolves to a boolean.

{
  path: ...,
  canLoad: [CanLoadGuard],
  loadChildren: ...
}
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