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On 13 December 2016 Angular 4 was announced, skipping 3 to avoid confusion due to the misalignment of the router package’s version which was already distributed as v3.3.0. The final version was released on March 23, 2017. Angular 4 is backward compatible with Angular 2.
Angular version 4.3 is a minor release, meaning that it contains no breaking changes and that it is a drop-in replacement for 4.x.x.
Features in Angular version 4.3 are:
Angular (commonly referred to as “Angular 2+” or “Angular 2“):
Is a TypeScript-based open-source front-end web application platform bed by the Angular Team at Google and by a community of individuals and corporations to address all of the parts of the developer’s workflow while building complex web application. Angular is a complete rewrite from the same team that built AngularJS.
AngularJS is a structural framework for dynamic web apps. It lets you use HTML as your template language and lets you extend HTML syntax to express your application’s components clearly and succinctly. AngularJS data binding and dependency injection eliminate much of the code you would otherwise have to write. And it all happens within the browser, making it an ideal partner with any server technology.
AngularJS is what HTML would have been, had it been designed for applications. HTML is a great declarative language for static documents. It does not contain much in the way of creating applications, and as a result building web applications is an exercise in.
The impedance mismatch between dynamic applications and static documents is often solved with:
A library – a collection of functions which are useful when writing web apps. Your code is in charge and it calls into the library when it sees fit. E.g., jQuery.
Frameworks – a particular implementation of a web application, where your code fills in the details. The framework is in charge and it calls into your code when it needs something app specific.
E.g., durandal, ember, etc.
AngularJS takes another approach. It attempts to minimize the impedance mismatch between document centric HTML and what an application needs by creating new HTML constructs. AngularJS teaches the browser new syntax through a construct we call directives.
Angular was a ground-up rewrite of AngularJS and has many unique features.
Angular also includes the benefits of ES6:
Angular 4 contains some additional Enhancement and Improvement.
Consider the following enhancements:
Angular 2 apps will work using Angular 4 without changing anything. Angular 4 offers lots-of enhancements i.e.
The HTTP Interceptors are used to Set Http Headers Request in Angular 4 using the import from “@angular/common/http”. The HTTP Interceptors are available in Angular 4.x versions.
The HTTP Interceptors are not supported in Angular 2. We are creating the Http Client Injectable class to achieve this. You can see the below examples for set http headers request with and without HTTP interceptors.
The Interceptors is a common used to set default headers for all responses.
The for Root is a static method and it’s very easy for developers to configure the modules and the best example is – RouterModule.for Root.
The Router Module also offers a for Child. It’s also a static method and use to configure the routes of lazy-loaded modules. The for Root and for Child are the traditional names for methods that configure services in root.
Angular 2 – ngFor vs. ngFor:
We can add the declarable classes like components, directives and pipes in the module’s declarations list and we can add only – components, directives and pipes classes in the @NgModule.
We do not declare – Module, Service, objects, strings, numbers, functions, entity models, configurations, business logic, and helper classes in the module’s declarations.
Two types of error:
In the both cases – We are using Http Error Response and return the useful information on what went wrong in this call!
In Annular, the following Steps are used to building authentication and authorization for RESTful APIs and applications. It might help you –
There are several open source libraries are available for angular which are helps with JWTs and has the ability to Decode the JWT, Authorization header to XHR requests and so on.
JSON Web Token (JWT) is an open standard which used for securely transmitting information between parties as a JSON object.
The JWTs can be signed with –
There are some scenarios where we can used JSON Web Tokens –
The JSON Web Tokens consist of three parts separated by dots (.), which are:
There are 4 different types of decorators:
A decorator is a function that is invoked with a prefix “@” symbol and is immediately followed by a class, parameter, method, or property. A decorator returns the same thing which was given as an input but in an augmented form.
Components are just simple classes which are declared as components with the help of component decorators.
It becomes easy to create an application which already works, with the help of angular CLI commands. “Ng generate” is used to generate components, routes, services, and pipes. Simple test shells are also created with the help of this CLI command. For generating a component in angular4 with the help of CLI command.
you need to follow the following syntax-
It generates the component and adds the component to module declarations.
Here are the elements which are present in the component directory structure anf modules: –
Module.ts- in this, the angular module is declared. @NgModule decorator is used which initializes the different aspects of angular applications. AppComponent is also declared in it.
Components.ts- it simply defines the components in angular and this is the place where the app-root sector is also defined. A title attribute is also declared in the component.
Component.html- it is the template file of the application which represents the visual parts of our components.
The ngFor directive instantiates a template for every element of the given iterator. The different local variables of the ngFor directive can be used in iterations. The ngFor directive can even be used with the HTML elements. It also performs various changes in DOM. Several exported values can be aliased to local variables with the help of ngFor directive. It allows us to build data presentation lists and tables in our HTML templates.
Here’s an example of ngFor directive with the help of HTML:
<tr *ngFor=”hero of heroes”>
Basically property binding means passing data from the component class and setting the value of a given element in the view. It is a one way binding in which the data is passed from component to the class. It allows us to control the element property values from component to class. Property binding in angular can take place by three ways:
Interpolation can be used to define a value, as long as the value being defined is a string.
Wrapping brackets around the element property and binding it to the component property is the most common type of property binding.
The third way is by adding “bind” before the element property.
The ngIf is a built-in template directive which is used to add or remove some parts of DOM. This addition or removal depends on the expression being true or false.
If the expression is evaluated to false, then the ngIf directive removes the HTML element. If the expression is evaluated to be true, then the element gets added to the DOM.
In angular js, there are differences between the meta-data annotations. Some of the differences are:
As the name implies, unit test is all about testing individual units of code. In order to answer some questions, isolating the unit of code under test is really important. When we do this, we are not forced into creating related pieces such as DOM elements for sorting. With the help of isolated unit tests, it becomes easier to implement everything. To simulate the requests, dependency injections are also provided. The individual sort function can be tested in isolation. And not only the sort function, any function can be tested in isolation.
NgRoute module is used when you want to navigate through different pages of your application but you also want your application to be a single page application. This ngRoute module navigates through different pages of your application without reloading the entire application. The angular js route module should be included to make your application ready for routing. The ngRoute is added as a dependency in the application. The routing engine captures the specific url requested by the user and renders the view based on the defined routing rules.
Services in angular js are used to organize and share code across your application. These are the suitable objects which are wired together with the help of dependency injection. The angular js services are lazily instantiated. The service is only instantiated by angular js only when the application component depends on it. In angular js, new services can be made or can even be used in other built-in services. Over 30 built-in services are present in angular js.
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