Thế Giới Giải Mã: Angular 2

Có nhiều cách để tăng hiệu suất cho ứng dụng Angular. Dưới đây là một số gợi ý:

Sử dụng AOT (Ahead-of-Time) Compilation: AOT Compilation giúp giảm thời gian tải ứng dụng và tăng tốc độ khởi chạy bằng cách biên dịch mã nguồn Angular thành mã máy trước khi chạy ứng dụng.

Lazy Loading: Sử dụng Lazy Loading để tải các module và component chỉ khi cần thiết, giúp giảm thời gian tải trang và tăng tốc độ chuyển đổi giữa các trang.

Sử dụng ChangeDetectionStrategy.OnPush: Đặt ChangeDetectionStrategy.OnPush cho các component để chỉ chạy kiểm tra thay đổi khi có sự thay đổi đầu vào từ phía component cha hoặc khi sự thay đổi được kích hoạt bằng cách sử dụng @Input hoặc async pipe. Điều này giúp giảm số lần kiểm tra thay đổi và tăng hiệu suất.

Sử dụng TrackBy trong vòng lặp *ngFor: Khi sử dụng vòng lặp *ngFor để hiển thị danh sách, hãy sử dụng trackBy để chỉ định một hàm xác định duy nhất cho mỗi mục trong danh sách. Điều này giúp Angular xác định các mục đã thay đổi và chỉ cập nhật các mục thay đổi thực sự, giúp tăng hiệu suất.

Sử dụng OnPush và Immutable Data: Sử dụng cơ chế OnPush và sử dụng dữ liệu bất biến (immutable data) để giảm số lần kiểm tra thay đổi và tăng hiệu suất.

Tối ưu hóa CSS: Loại bỏ CSS không sử dụng, sử dụng CSS minification và sử dụng các kỹ thuật như CSS Sprites để tối ưu hóa tải trang.

Sử dụng Web Workers: Sử dụng Web Workers để chạy các tác vụ nặng như tính toán phức tạp hoặc xử lý dữ liệu lớn trong một luồng riêng biệt, giúp tránh làm đóng băng giao diện người dùng.

Sử dụng Lazy Loading Images: Sử dụng kỹ thuật lazy loading để tải ảnh chỉ khi cần thiết, giúp giảm thời gian tải trang ban đầu.

Tối ưu hóa HTTP Requests: Sử dụng HTTP Interceptors để tối ưu hóa các yêu cầu HTTP bằng cách thêm caching, nén dữ liệu hoặc sử dụng HTTP/2.

Sử dụng Production Build: Sử dụng production build để tạo ra phiên bản tối ưu hóa của ứng dụng Angular, bao gồm việc loại bỏ mã không sử dụng và tối ưu hóa kích thước tệp tin.

Nhớ rằng, việc tăng hiệu suất không chỉ dừng lại ở việc áp dụng các kỹ thuật tối ưu hóa, mà còn phụ thuộc vào cấu trúc và thiết kế của ứng dụng.

What is Angular

The Angular is a development platform for building a Single Page Application for mobile and desktop. It uses Typescript & HTML to build Apps. The Angular itself is written using the Typescript. It now comes with every feature you need to build a complex and sophisticated web or mobile application. It comes with features like component, Directives, Forms, Pipes, HTTP Services, Dependency Injection, etc

Angular Versions

The early version of the Angular was named as Angular 2. Then later it was renamed to just Angular. Then Angular Team releases new versions of the Angular versions Regularly and the last stable version that is available in Angular 10.0.12

The Angular 9 is released on 06.02.2020. The Angular 9 is a major release. This release switches to ivy compiler and runtime by default. The ivy brings smaller bundle sizes, faster & better testing debugging, Improved type checking, build times, etc

Angular 10 is released on 24-06-2020. You can learn about the list of features from this link

Version History

Angular Version	Date	Description
Angular 2	14.09.2016	Initial Version of Angular
Angular 4	23.03.2017	Version 4
Angular 5	11.11.2017	Version 5
Angular 6	03-05-2018	Version 6
Angular 7	18-10-2018	Version 7
Angular 8	25-08-2019	Version 8
Angular 9	06-02-2020	Version 9
Angular 10	24-06-2020	Version 10
Angular 10.0.12	24-08-2020	Version 10.0.12

You can read the latest versions at https://github.com/angular/angular/blob/master/CHANGELOG.md

Prerequisites

The Angular tutorial requires a working knowledge of Javascript, HTML & CSS. It also requires the concept of OOP.

We are going to use Typescript as our language. If you have knowledge of C# or Java, then you would find it very easy. Take a look at the Typescript Tutorial

Angular Tutorial

Introduction to Angular

This Introduction to Angular Tutorial gives you a glimpse of Angular. Angular is a UI framework for building mobile and desktop web applications. It is built using Javascript. Using Angular you can build amazing client-side applications using HTML, CSS, and Typescript. It is very important to know how the Angular framework works before you start using it. The following tutorials introduce you to Angular and discuss Angulars architecture.

Getting Started With Angular Tutorial

The Angular has gone through a lot of changes since the version Angular 2. From the Angular 7 version, installing and creating a new project in angular has become very simple. The only thing you need to do in install and Visual Studio code, NPM Package manager & Angular CLI. Once, you install the required dependencies, creating a new project is as easy as running a simple command ng new. Angular CLI takes care of Configuration & initialization of various libraries.

The following step by step tutorial will take you through the process of creating an Angular application

Components

The Component is the main building block of an Angular Application. A Component contains the definition of the View and the data that defines how the View looks and behaves. The Angular Components are plain javascript classes and defined using @component Decorator. This Decorator provides the component with the View to display & Metadata about the class

The Component passes the data to the view using a process called Data Binding. This is done by Binding the DOM Elements to component properties. Binding can be used to display component class property values to the user, change element styles, respond to a user event, etc.

Directives

The Angular directive helps us to manipulate the DOM. You can change the appearance, behavior, or layout of a DOM element using the directives. They help you to extend HTML. The Angular directives are classified into three categories based on how they behave. They are Component, Structural and Attribute Directives

The ngFor is an Angular structural directive, which repeats a portion of the HTML template once per each item from an iterable list (Collection). The ngSwitch allows us to Add/Remove DOM Element. It is similar to the switch statement of Javascript. The ngIf allows us to Add/Remove DOM Element.

The ngClass Directive is an Angular Attribute Directive, which allows us to add or remove CSS classes to an HTML element. The ngStyle directive allows you to modify the style of an HTML element using the expression. Using the ngStyle you can dynamically change the style of your HTML element.

Pipes

The Angular pipes are used to Transform the Data. For Example, the Date pipe formats the date according to locale rules. We can pass arguments to pipe and chain pipes. The Angular also allows us to create the Custom Pipe

Component Communication

Component Life Cycle Hook

The life cycle hooks are the methods that angular invokes on directives and components as it creates, changes, and destroys them. Using life-cycle hooks we can fine-tune the behavior of our components during creation, update, and destruction.

Angular Forms

The data entry forms can be very simple to very complex. The Forms contain large no of input fields, a variety of fields like Text boxes, Dates, Numbers, Emails, Password, Check Boxes, Option boxes, etc. These fields can Span multiple tabs or multiple pages. Forms may also contain complex validation logic interdependent on multiple fields.

The Angular forms modules are designed to handle all of the above and a lot more. The Angular Forms now supports Reactive forms approach to Forms development. The older way of Template-based approach is also supported

Services & Dependency Injection

Services allow us to create reusable code and use it every component that needs it. The Services can be injected into components and other services using the dependency injection system. The dependencies are declared in the Module using the Provider’s metadata. The Angular creates a tree of injector & Providers that resembles the Component Tree. This is called the hierarchical pattern.

Angular Forms Validation

One of the common tasks that is performed, while building a form is Validation. The Forms Validation is built into the Angular Forms Module. The Angular provides several Built-in validators out of the box. If those validators do not fit your needs, then you can create your own custom validator.

HTTP

The newly designed HttpClient Module allows us to query the Remote API source to get data into our Application. It requires us to Subscribe to the returned response using RxJs observables.

Angular Router

The Router module handles the navigation & Routing in Angular. The Routing allows you to move from one part of the application to another part or one View to another View.

Angular Module

The Angular Modules help us to organize our code into manageable parts or block. Each block implements a specific feature. The Components, Templates, Directives, Pipes, and Services, which implements that feature become part of the module. The following tutorial explains, how best you can create an Angular Module, The folder structure that you can use, etc. We can also load the Modules lazily or Preload thus improving the performance of the Application.

Advanced Components

The Components in Angular are very powerful feature. The following tutorials take you through some of the important features of the Angular Component.

Observable in Angular

The Angular uses the Observable Pattern extensively. The following tutorials gives you an introduction to observable and how to use it in an Angular Application.

Styling the Application

The Angular uses several different ways to style the Application. You can style the app globally and then override it locally in the component very easily. The component styles have local scope, which is achieved using the various View Encapsulation strategies. Learn all these in the section

Others

Location Service

Configuration

The apps usually need some sort of Run-time configuration information like URL endpoint etc, which it needs to load at startup. Also, different environments like development, production & testing require different environments, etc.

Handling Errors

In the following Angular tutorials, we look at how Angular handles the error. We handle errors by setting up a Global Error handler or custom error handler. Also,.whenever the error occurs in an HTTP operation, the Angular wraps it in an httpErrorResponse Object. Learn how to handle the HTTP Errors also.

Angular CLI

Learn how to use Angular CLI to speed up the development of Angular Application

SEO & Angular

You Website is useless if it is not found by the Search Engines. There are many things you must consider to make App SEO friendly. You need to set up Title & Meta Tags for each page. Ensure that the search engines can crawl and read your page. Set the correct Canonical URL for each page etc. Also, ensure that the app loads quickly, etc. The Following Angular Tutorials guides you through some of the important SEO features.

Angular Universal

The following Angular Universal Tutorial explains how to achieve Server Side Rendering using Angular Universal. The rendering the App on the server side makes it load quickly and also ensures that the search engines can crawl the content

Server-Side Rendering Angular Universal Tutorial

Building & Hosting

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Angular Resources

Angular how-to guides

Module Loaders

The Angular application can use either SystemJs or Webpack module loader. We will demonstrate how to make use of both the Loader by building a small application.

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