An Ultimate guide on Angular Directives and their types

Safalta Expert Published by: Aryan Rana Updated Thu, 01 Dec 2022 11:10 PM IST

The most crucial part of an Angular application may be its directives, and the component—the most popular Angular unit—is a directive. The only additional thing an Angular component has is a directive with a template. When we refer to components as the foundation of Angular applications, what we mean is that Angular applications are built on directives.
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Table of Content
Angular Directives
Types of Angular directives
Using the Existing Angular Directives
Creating an attribute directive
Angular directives: an example of an attribute directive

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Source: Safalta

Attribute Angular Directives">Structural vs. Attribute Angular Directives

Angular Directives

A directive's fundamental component is a function that runs whenever the Angular compiler identifies it in the DOM. By adding new syntax, Angular directives are used to increase the power of HTML. Each directive has a name, either one that is predefined by Angular, such as ng-repeat, or a custom name that can be anything. Each directive also specifies where it can be applied, whether it be in an element, attribute, class, or comment.

Types of Angular directives

Angular directives are typically divided into two categories, starting with version 2 and later:

As we already saw, components are nothing more than directives with templates. They give us a cleaner way to define them because they operate behind the scenes with the directive API. There are no templates for the other two directive types. Instead, they are designed especially for DOM manipulation.

  • Attribute directives

The DOM is manipulated by attribute directives, which alter its behavior and appearance. Attribute directives are used to dynamically alter a component's behavior in response to changing properties, apply conditional styling to elements, show or hide elements, and more.

  • Structural directives

These are designed specifically to create and remove DOM elements. The DOM is essentially kept intact by some attribute directives, such as hidden, which shows or hides an element. However, because they partially or entirely remove elements from the DOM, structural Angular directives are much less DOM-friendly. We must therefore exercise extra caution when using these since we are altering the HTML structure.

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Using the Existing Angular Directives

If you've previously created an Angular application, you've probably used the existing directives because using them is fairly simple. It's very easy to use the directives in Angular. The ability to design our Angular directives gives them their true power. The following sections will focus on Angular's clear and straightforward API for building custom directives.

Creating an attribute directive

It's similar to creating a component to create a directive. However, we employ the @Directive decorator in this instance. For instance, you could design a directive called "my-error-directive" that will make an element's background red to signify an error. We can use the directive after importing it from @angular/core. We first require a selector, which gives the directive a name. We refer to this situation as "my error. We must follow best practices and name our Angular directives with a prefix. By doing so, we can be certain to steer clear of any conflicts with common HTML attributes. The ng prefix should also not be used. We don't want to confuse our specially created Angular directives with the Angular predefined ones, as those are used by Angular. 

Angular directives: an example of an attribute directive

  • Creating a structural directive

The method for developing structural behavior is the same as before. The directive's code is first created in a new file, added to the declarations, and then used in the component.

When we need to display different information to different users based on their permissions, the kind of approach provided by structural directives can be very helpful. A site administrator, for instance, should have access to and be able to edit everything, but a regular user shouldn't. The common user, and all users, would have access to private data if we loaded it into the DOM using an attribute directive.

Structural vs. Attribute Angular Directives

When should we use each option separately?

Because it solves our problems, we might use the incorrect solution if the answer is unclear. The right one can be selected, though, by following a straightforward rule. We should keep the element with the directive if it will still be useful in the DOM when the DOM is hidden. In this instance, we employ a hidden attribute directive. But if the element is useless, we should get rid of it. But we must exercise caution to stay clear of some common pitfalls. The trap of always hiding elements just because it's simpler must be avoided. The DOM will become significantly more complex as a result, which will probably affect its overall performance. Another mistake to avoid is constantly deleting and adding components. Sure, it's cleaner, but performance suffers as a result. Overall, each situation should be carefully examined because the best course of action is always the one that has the least overall impact on the structure, functionality, and performance of your application. Attribute directives, structural directives, or—in the most typical case—a combination of the two—might be the answer.

The central component of Angular applications, Angular directives, was the subject of this article. We examined the various directive categories and learned how to design special ones that meet our requirements.



What do Angular directives mean?

Directives in Angular are described as classes that can change or add new behavior to the template's elements. Adding new elements, removing elements, or altering the appearance of the DOM elements are all examples of how directives in Angular can be used to move the DOM.



How do Angular directives function?

By adding new syntax, Angular directives are used to increase the power of HTML. Each directive has a name, either one that is predefined by Angular, such as ng-repeat, or a custom name that can be anything.



What is the Angular DOM?

The document object model is referred to as DOM. Application data is connected to HTML DOM elements' attributes using AngularJS's directives.

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