Question: What Is @ViewChild In Angular?

What is ViewChild and ViewChildren in angular?

The @ViewChild and @ViewChildren decorators in Angular provide a way to access and manipulate DOM elements, directives and components.

You can use ViewChild if you need to query one element from the DOM and ViewChildren for multiple elements..

What is a decorator in angular?

Decorators are a design pattern that is used to separate modification or decoration of a class without modifying the original source code. In AngularJS, decorators are functions that allow a service, directive or filter to be modified prior to its usage.

What is EventEmitter in angular?

EventEmitter is an angular2 abstraction and its only purpose is to emit events in components. Quoting a comment from Rob Wormald. […] EventEmitter is really an Angular abstraction, and should be used pretty much only for emitting custom Events in components. Otherwise, just use Rx as if it was any other library.

What is a selector in angular?

What is a Selector in Angular? A selector is one of the properties of the object that we use along with the component configuration. A selector is used to identify each component uniquely into the component tree, and it also defines how the current component is represented in the HTML DOM.

What is an EventEmitter?

An event emitter is a pattern that listens to a named event, fires a callback, then emits that event with a value. Sometimes this is referred to as a “pub/sub” model, or listener.

What does $event mean in angular?

When a user interacts with an application in the form of a keyboard movement, a mouse click, or a mouseover, it generates an event. … These events need to be handled to perform some kind of action.

What is ng template in angular?

ng-template is an Angular element used to render HTML templates. We use ng-template with angular *ngIf directive to display else template.

What is ElementRef in angular?

According to the official docs. Angular ElementRef is a wrapper around a native element inside of a View. It’s simply a class that wraps native DOM elements in the browser and allows you to work with the DOM by providing the nativeElement object which exposes all the methods and properties of the native elements.

What is RxJS in angular?

RxJS (Reactive Extensions for JavaScript) is a library for reactive programming using observables that makes it easier to compose asynchronous or callback-based code. See (RxJS Docs). … The library also provides utility functions for creating and working with observables.

Is EventEmitter observable?

This means that the EventEmitter class is essentially an RxJS observable stream. Which, of course, means that we should be able to operate on it and subscribe to it just like we would any other RxJS stream.

What is TemplateRef and ViewContainerRef?

TemplateRef : It represents an embedded template that can be used to instantiate embedded. ViewContainerRef: It represents a container where one or more views can be attached.

What is HostListener in angular?

HostListenerlink Decorator that declares a DOM event to listen for, and provides a handler method to run when that event occurs. … A set of arguments to pass to the handler method when the event occurs.

What is meta data in angular?

Metadata is used to decorate a class so that it can configure the expected behavior of the class. … The component decorator is used to declare the class in the app. component. ts file as a component.

What is the difference between ViewChild and ContentChild?

It is used to access Child Component in the Parent Component. Any directive, component, and element which is part of component template is accessed as ViewChild. Whereas, any element or component which is projected inside is accessed as ContentChild.

What is the use of @ViewChild in angular?

The @ViewChild decorator allows us to inject into a component class references to elements used inside its template, that’s what we should use it for. Using @ViewChild we can easily inject components, directives or plain DOM elements.

What is the difference between @component and @directive in angular?

Component is a directive which use shadow DOM to create encapsulate visual behavior called components. … Directives is used to add behavior to an existing DOM element. Component is used to break up the application into smaller components. Directive is use to design re-usable components.

What is ViewContainerRef in angular?

ViewContainerRef represents a container where one or more views can be attached. The first thing to mention here is that any DOM element can be used as a view container. What’s interesting is that Angular doesn’t insert views inside the element, but appends them after the element bound to ViewContainer .

What is static in ViewChild?

The static option for @ViewChild() and @ContentChild() queries determines when the query results become available. With static queries (static: true), the query resolves once the view has been created, but before change detection runs.