Table of Contents
What is the use of ViewChild in angular?
ViewChildlink Property decorator that configures a view query. The change detector looks for the first element or the directive matching the selector in the view DOM. If the view DOM changes, and a new child matches the selector, the property is updated.
What is HostListener and HostBinding?
@HostBinding and @HostListener are two decorators in Angular that can be really useful in custom directives. @HostBinding lets you set properties on the element or component that hosts the directive, and @HostListener lets you listen for events on the host element or component.
What do you mean by directives?
: something that serves to direct, guide, and usually impel toward an action or goal especially, government : an authoritative order or instrument issued by a high-level body or official a presidential directive.
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.
What is HostBinding angular?
HostBindinglink Decorator that marks a DOM property as a host-binding property and supplies configuration metadata. Angular automatically checks host property bindings during change detection, and if a binding changes it updates the host element of the directive.
What is @input and @output in angular?
A common pattern in Angular is sharing data between a parent component and one or more child components. @Input() allows a parent component to update data in the child component. Conversely, @Output() allows the child to send data to a parent component.
What is a ViewChild?
A ViewChild is a component, directive, or element as a part of a template. If we want to access a child component, directive, DOM element inside the parent component, we use the decorator @ViewChild() in Angular. Since the child component can be located inside the parent component, it can accessed as @ViewChild.
What is ContentChild and ContentChildren?
ContentChildren is different from the ContentChild . ContentChild always returns the reference to a single element. If there are multiple elements the ContentChild returns the first matching element, ContentChildren always returns all the matching elements as a QueryList.
How do I pass data from one component to another in angular 8?
in the parent component:
- Import ViewChild() and ngAfterViewInit() and implement the lifecycle hook. import { ViewChild, AfterViewInit } from ‘@angular/core’;
- Import the child component.
- Use the @ViewChild() directive.
- Declare a variable that holds the data.
- In ngAfterViewInit() call the variable that holds the data.
What is TemplateRef in angular?
TemplateReflink Represents an embedded template that can be used to instantiate embedded views. To instantiate embedded views based on a template, use the ViewContainerRef method createEmbeddedView() .
What is a pipe angular?
Pipes are a useful feature in Angular. They are a simple way to transform values in an Angular template. There are some built in pipes, but you can also build your own pipes. A pipe takes in a value or values and then returns a value.
What is the difference between ViewChild and ContentChild?
What is the difference between @ViewChild and @ContentChild ? ViewChild is used to select an element from component’s template while ContentChild is used to select projected content.
How many types of directives are there?
The three types of directives in Angular are attribute directives, structural directives, and components. You read that right — Angular components are actually just directives under the hood. So what makes them different from the other two types of directives? Components are directives that have a template.
What is AfterViewInit in angular?
AfterViewInitlink A lifecycle hook that is called after Angular has fully initialized a component’s view. Define an ngAfterViewInit() method to handle any additional initialization tasks.
What are directives in JSP?
JSP directives are the messages to JSP container. They provide global information about an entire JSP page. JSP directives are used to give special instruction to a container for translation of JSP to servlet code. Directives can have many attributes by comma separated as key-value pairs.
What is ViewChild static?
The static option for @ViewChild() and @ContentChild() queries tells that 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.
What is component directives in angular?
Component Directives: It forms the main class and is declared by @Component. It contains the details on component processing, instantiated and usage at run time. Example: It contains certain parameters some of them are shown in this example.
What is directive sentence?
an order or change that comes from an authority figure typically in charge of a group of people. Examples of Directive in a sentence. 1. The School Board created a new directive for all teachers to complete 300 hours of instruction for teaching a foreign language.
What is directives in angular?
Directives are custom HTML attributes which tell angular to change the style or behavior of the Dom elements. When we say that components are the building blocks of Angular applications, we are actually saying that directives are the building blocks of Angular applications.
What are the types of directives?
Components—directives with a template. This type of directive is the most common directive type. Attribute directives—directives that change the appearance or behavior of an element, component, or another directive. Structural directives—directives that change the DOM layout by adding and removing DOM elements.
What is use of @ViewChild?
Conclusion. 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 opposite of Directive?
Antonyms of DIRECTIVE disorganization, lawlessness, suggestion, proposal, entreaty, recommendation, petition, answer, appeal, plea, following, urging.
What is QueryList in angular?
QueryList is just a fancy name for an object that stores a list of items. What is special about this object is when the state of the application changes Angular will automatically update the object items for you.
Why directives are used in angular?
Angular directives are used to extend the power of the HTML by giving it new syntax. Each directive has a name — either one from the Angular predefined like ng-repeat , or a custom one which can be called anything. And each directive determines where it can be used: in an element , attribute , class or comment .