Mastering Angular.js Lifecycle Hooks: Achieve 20% Development Efficiency

One of the most well-liked and trustworthy open-source application design frameworks available today, Angular is used by developers all over the world to create complex and effective online applications.

This TypeScript-written JavaScript development framework and platform are kept up to date by Google. Data visualization and single-page client applications are the two main uses for Angular. A unique feature called "angular lifecycle hooks" enables us to "hook into" and execute code at a particular directive or component lifecycle event.

The following subjects are going to be covered in this article: Angular parts and their constituents, Hooks for the life cycle of an angular component and the various kinds of such hooks.

Gaining more knowledge on these subjects will improve your comprehension of the functionality of Angular frameworks, as well as the lifecycle of an Angular component and hooks.

You should read this article through to the end if you want to gain a deeper understanding of Angular.

An Angular Component: What Is It?

What is an angular component? Developers use different analogies to explain Angular components.

But for a more precise component definition, we still like to use the Lego blocks. You will need to select and use various block pieces when building a Lego structure, such as a basic house. In order to create the desired design and a final product that is well-structured, you must also stack them correctly.

Each of these components is regarded as an essential component of the Lego house you are designing since it is a part of the overall structure. Any of them being absent or any modifications you make would affect the finished product.

Angular components can also be used in a similar situation. The UI of an Angular application is composed of the Angular components, much like the Lego house structure is made up of block pieces, as we have discussed.

The building blocks of an application, known as components, define the various UI elements, represent a section of a view, and make up an Angular application. The data and logic for user interaction that determine the look and feel of the view are contained in angular components.

A @Component ( ) decorator, an HTML template, and styles make up each component. The class's metadata, as well as the template or view that will be displayed, are defined by the decorator. Additionally, it gives the component particular data such as:

• CSS Selector: The way the component is used in a template is explained by the CSS selector.
• HTML Template: What appears on the page and how the component should be rendered are specified in the HTML template.

  Despite having a similar appearance to standard HTML code, the HTML template is somewhat different because it has extra Angular-specific syntax that allows it to interact and connect with the component class.

• Typescript Class: Finally, the Typescript class is compiled into JavaScript, outlining its behavior.

  It also contains the properties that hold data and the methods that specify the component's logic.

• Optional CSS Styles: The optional set of CSS styles defines the HTML elements of the template.

After a quick overview of Angular's elements and components, let's move on to our next topic; Angular component lifecycle hooks.

However, let's first quickly review what an Angular component lifecycle is before moving on to the Angular lifecycle hooks.

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An Angular Component Lifecycle: What Is It?

As we have discussed previously, the fundamental building block of any Angular application is its components. Every one of these elements has a unique lifespan.

The components experience eight distinct phases during the Angular lifecycle. Every life cycle begins with initialization and concludes with destruction. Angular itself oversees and manages each of these components, which is an intriguing aspect.

Angular generates heirs, instantiates the component class, and creates and presents its root components, all during the initialization phase.

Subsequently, Angular generates the component and child views. From then on, the lifecycle of Angular components keeps changing. Angular will continuously monitor and assess the components for modifications to data-bound properties, such as input properties, data bindings, and expressions, during the app development process.

The anticipated content will also be rendered by it. Angular updates both the view and the component instance when it detects changes and when necessary.

A component instance enters the death stage, which signifies the end of its life cycle once it is no longer required and in use. In the interim, Angular will destroy this component instance and remove its rendered template from the Document Object Model.

Also Read: Responsive Angular.js: Enhancing Mobile Performance by 30%

Angular Component LifeCycle Hooks: What Are They?

Simple functions known as "angular component lifecycle hooks" describe the various stages that an angular component goes through.

As it creates, modifies, and destroys components during execution, the life cycle hooks are also thought of as a method by which the Angular development platform calls upon the directives and components when a specific event takes place. It is also regarded as a callback function that the platform activates whenever a component experiences a happy event.

The AngularJS Developers also use the term "Angular lifecycle hooks'' to indicate or highlight particular moments or phases in a component's life, particularly when developing an Angular application.

It facilitates the alteration and refinement of the behavior of the app components by developers throughout the creation, update, destruction, and modification of the Angular component lifecycle.

The lifecycle hooks in an Angular application can be used to monitor, comprehend, and assess significant events in a component's life.

Better change detection and initialization of new component instances are made possible by this. In addition, the angular hooks assist in cleaning up before deleting the component instances from the DOM and in tapping events to react to updates when necessary during change detection.

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Various Angular Component Lifecycle Hook Types

The angular component lifecycle comprises eight distinct hooks. These are the following:

• ngOnChanges

The callback method known as the ngOnChanges life cycle hook is triggered whenever the component's input control is altered, or the data-bound property is modified.

The Angular lifecycle hooks are triggered prior to ngOnInit and react to changes made to data-bound input properties. It is given a modified SimpleChanges object or data map that has the data-bound property's values or previous and current positions.

Keep in mind that if the component has input, Angular will only call the ngOnChanges Angular life cycle hooks. As long as the components have input, you can use it in any component.

• ngOnInit

After the component has been created, set, and introduced with its input values or properties, Angular initializes the ngOnInit Angular lifecycle hook.

Additionally, as Angular displays the data-bound properties and after ngOnChanges, this Angular lifecycle hook is called. Initializing data or logic for a component is done via the ngOnInit lifecycle hook. By default, the Angular CLI adds this hook to the lifecycle of Angular components.

These angular hooks are only called once, so please be aware of that. Angular is still able to call ngOnInit even in the absence of calling ngOnChanges first. This is valid in situations where the component lacks template-bound inputs as well as situations where ngOnChanges cannot be called.

ngOnInit is called in this instance following the constructor.

• ngDoCheck

Every cycle of change detection involves the invocation of these Angular lifecycle hooks. Even Angular is unable to identify and respond to changes that it is able to detect.

It is also possible to invoke the ngDoCheck hook in the absence of any modifications to the input properties. It is called immediately following ngOnInit and ngOnChanges.

• ngAfterContentInit

The ngAfterContentInit Angular lifecycle hooks are likewise only called once during the component's lifetime, similar to ngOnInit.

Angular calls ngAfterContentInit immediately following the initial ngDoCheck.The ngAfterContentInit Angular lifecycle hooks initialize the content. As soon as the external content is projected into the component's field of view, it reacts. Even in the absence of any content to the project, it can still be called.

• ngAfterContentChecked

Similar to the ngAfterContentInit hook, the ngAfterContentChecked hook is called following the external content's initialization, verification, and update.

ngAfterContentChecked Angular lifecycle hooks are called during each change detection cycle, following the content project's check-in to the component or following the full initialization of the component's view and child views. These Angular lifecycle hooks are called following each iteration of ngDoCheck, ngAfterContentInit, and each cycle of change detection.

• ngAfterViewInit

Additionally, these Angular lifecycle hooks are only called once in the first change detection cycle-that is, following ngAfterContentChecked and the initialization of the component's view and child views.

• ngAfterViewChecked

Angular will call the ngAfterViewChecked hook once it has finished verifying the component's view and child views.

Every ngAfterContentChecked and ngAfterViewInit in between are followed by ngAfterViewChecked. Only Angular components can use these Angular lifecycle hooks.

• ngOnDestroy

The phase of destruction is where the components that are no longer in use end up, as we have already discussed.

When Angular has fully destroyed such components, it will invoke the ngOnDestroy lifecycle hook. This is the ideal time to use the clean-up logic, disconnect from any event handlers, and unsubscribe from all observables if necessary.

You can significantly reduce the likelihood of memory leaks in the future by putting these procedures into place while the ngOnDestroy Angular lifecycle hooks are in effect.

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Conclusion

Angular directives can also be used with the lifecycle hooks we covered earlier. Please be aware that before you begin working with the Angular component lifecycle hooks, you must first learn and comprehend the fundamentals of TypeScript programming.

You also need to have a basic understanding of the processing steps of the component lifecycle and the principles of Angular app design. It is important to understand that not every project requires every one of these angular hooks. You may not need to use and adhere to every one of the eight Angular lifecycle hooks for your project.

You must select the hooks carefully, making sure you only select those that are essential and appropriate for the kind of Angular application you are developing.

It would help if you made sure that the developers working on your app understand the significance of each Angular component for a more seamless process and a successful project. They need to be more knowledgeable about the various Angular lifecycle hooks and the functions they serve throughout the development of Angular apps.