What Is The Purpose Of Selector?

How does ngIf work in angular2?


A structural directive that conditionally includes a template based on the value of an expression coerced to Boolean.

When the expression evaluates to true, Angular renders the template provided in a then clause, and when false or null, Angular renders the template provided in an optional else clause..

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 nativeElement?

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 the use of selector in angular 7?

selector : A CSS selector that tells Angular to create and insert an instance of this component wherever it finds the corresponding tag in template HTML. For example, if an app’s HTML contains , then Angular inserts an instance of the HeroListComponent view between those tags.

What is @ViewChild in angular?

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.

How do I use ngIf?

The ngIf directive syntax looks like this:

Content to render when condition is true.
Content to render when condition is true. Content to render when condition is true.

Can we use ngIf and ngFor together?

You’ll try to put both an *ngFor and an *ngIf on the same host element. Angular won’t let you. You may apply only one structural directive to an element. … Prohibiting multiple structural directives makes them moot.

What is the use of selector in angular?

The selector is a property inside the angular component which identifies the directive in a template and triggers instantiation of the directive. The selector has to be unique so that it doesn’t override already existing element or component available by a number of third-party packages.

What is @input in angular?

Use the @Input() decorator in a child component or directive to let Angular know that a property in that component can receive its value from its parent component. … So an @Input() allows data to be input into the child component from the parent component.

How do I check ngIf condition?

AND condition in *ngIf We can use multiple conditions in *ngIf with logical operator AND (&&) to decide the trustworthy of *ngIf expression. If all conditions are true, then element will be added to the DOM.

What is a selector DJ?

Back in 1950s Jamaica, selectors were what we might refer to in the modern day as a dance music DJ, essentially marrying the term to this art form. In essence, it refers more to curating a selection of songs back-to-back and creating the illusion of non-stop music than to just simply jockey a disc.

What is a selector?

5.1 Pattern matching In CSS, pattern matching rules determine which style rules apply to elements in the document tree. These patterns, called selectors, may range from simple element names to rich contextual patterns. If all conditions in the pattern are true for a certain element, the selector matches the element.

What is pipe in angular?

Pipes are a useful feature in Angular. They are a simple way to transform values in an Angular template. … A pipe takes in a value or values and then returns a value. This is great for simple transformations on data but it can also be used in other unique ways.

What is a class selector?

The . class selector selects elements with a specific class attribute. To select elements with a specific class, write a period (.) character, followed by the name of the class. You can also specify that only specific HTML elements should be affected by a class.

How do I switch from CSS selector to XPath?

Open the page in a browser (for example, Chrome), right-click the element that you want to capture, and select Inspect to open the developers tools. From the Elements tab, right-click the element and select either Copy > Copy selector or Copy XPath.

What is difference between XPath and CSS selector?

Hello Ushma, the primary difference between XPath and CSS Selectors is that, with the XPath we can traverse both forward and backward whereas CSS selector only moves forward. Although CSS selectors perform far better than Xpath and it is well documented in Selenium community.

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() .

The reason is that the infrastructure used to generate the XPath, doesn’t guarantee that the XPath will remain the same between two different executions. … The recommended way would be to use id or any other stable element identifier, or to search for a parent element and then use the relative XPath from that element.

Is XPath slower than CSS?

On a whole, Internet Explorer is slower than the other drivers, but between CSS and XPath it looks like XPath is actually faster than CSS. … In some cases CSS is faster, and in others, XPath. And Firefox looks to be a bit more optimized for CSS since it’s mostly faster across the board.

Which is better CSS or Xpath?

CSS selectors perform far better than Xpath and it is well documented in Selenium community. … Xpath engines are different in each browser, hence make them inconsistent. IE does not have a native xpath engine, therefore selenium injects its own xpath engine for compatibility of its API.

What is Selector and its types?

Simple selectors (select elements based on name, id, class) Combinator selectors (select elements based on a specific relationship between them) Pseudo-class selectors (select elements based on a certain state) Pseudo-elements selectors (select and style a part of an element)

How do you use NG content?

That is the simplest way to explain what ng-content provides. You use the tag as a placeholder for that dynamic content, then when the template is parsed Angular will replace that placeholder tag with your content .

What is service in angular?

Angular services are singleton objects that get instantiated only once during the lifetime of an application. … The main objective of a service is to organize and share business logic, models, or data and functions with different components of an Angular application.