AngularJS is a JavaScript-based open-source front-end web framework. AngularJS is supervised by Google and by a community of individuals and corporations. This community focuses on addressing various challenges that occur while developing single-page applications. AngularJS is a structural framework for self-motivated web apps. With AngularJS, designers know how to use HTML as the template language and it authorizes for the extension of HTML's syntax to pass on the application's components effortlessly. Furthermore, AngularJS is usually related to SPA, that developers can use Angular to build any type of app, taking benefit of features such as two-way binding, templating, RESTful API handling, modularization, AJAX handling, dependency injection, etc.
AngularJS is a javascript framework used for creating single web page applications. It allows you to use HTML as your template language and enables you to extend HTML’s syntax to express your application’s components clearly
The key features of AngularJS are
Scope refers to the application model, it acts like glue between application controller and the view. Scopes are arranged in hierarchical structure and impersonate the DOM ( Document Object Model) structure of the application. It can watch expressions and propagate events.
In AngularJS services are the singleton objects or functions that are used for carrying out specific tasks. It holds some business logic and these function can be called as controllers, directive, filters and so on.
Like JavaScript, Angular expressions are code snippets that are usually placed in binding such as {{ expression }}
The key difference between the JavaScript expressions and Angular expressions
The angular modules collectively define an angular application where we can write the angular code.
Modules contain the different parts of an angular application. A module is created by angular.module function in angular.
Three directive scopes are available in AngularJs.
They are:
It is a part of the process of data binding in AngularJs. It compares the old and new version of the scope model value in each digest cycle.
The digest cycle is triggered automatically. We can also enhance the usability by using $apply (), if we want to trigger the digest cycle manually.
One-way binding is used to bind the data from the model to view without updating the HTML template or view automatically.
Thus in order to update the HTML template, we need to write a custom code which will update the view every time whenever a data is binded from model to view.
Whereas, two-way binding is used to bind the data from the model to view and vice versa(i.e view to model) by automatically updating the HTML template without writing any custom code.
Given below are the various differences.
SessionStorage – The data is stored for a particular session. The data will be lost whenever the browser tab will be closed or after some particular session. Maximum size stored can be up to 5MB.
LocalStorage – The data is stored with no expiration date. The data can only be cleared by JavaScript or by clearing the browser cache. Storage limit is maximum than the sessionStorage and cookie.
Cookies – It stores the data that has to be sent back to the server with some requests. The cookie's expiration varies on the type and duration set from either the server side or client side. Maximum size stored can be less than 4KB.
Templates in Angular are written with HTML that contains Angular-specific elements and attributes. These templates are combined with information coming from the model and controller which are further rendered to provide the dynamic view to the user.
String interpolation in Angular is a special syntax that uses template expressions within double curly {{ }} braces for displaying the component data. It is also known as moustache syntax. The JavaScript expressions are included within the curly braces to be executed by Angular and the relative output is then embedded into the HTML code. These expressions are usually updated and registered like watches, as a part of the digest cycle.
AOT stands for Angular Ahead-of-Time compiler. It is used for pre-compiling the application components and along with their templates during the build process. Angular applications which are compiled with AOT has a smaller launching time. Also, components of these applications can execute immediately, without needing any client-side compilation. Templates in these applications are embedded as code within their components. It reduces the need for downloading the Angular compiler which saves you from a cumbersome task. AOT compiler can discard the unused directives which are further thrown out using a tree-shaking tool.
jQlite is also known as jQuery lite is a subset of jQuery and contains all its features. It is packaged within Angular, by default. It helps Angular to manipulate the DOM in a way that is compatible cross-browser. jQLite basically implements only the most commonly needed functionality which results in having a small footprint.
Dependency Injection (DI) is a software design pattern where the objects are passed as dependencies rather than hard-coding them within the component. The concept of Dependency Injection comes in handy when you are trying to separate the logic of object creation to that of its consumption. The ‘config’ operation makes use of DI that must be configured beforehand while the module gets loaded to retrieve the elements of the application. With this feature, a user can change dependencies as per his requirements.
Transpiling in Angular refers to the process of conversion of the source code from one programming language to another. In Angular, generally, this conversion is done from TypeScript to JavaScript. It is an implicit process and happens internally.
In order to perform animation in an Angular application, you need to include a special Angular library known as Animate Library and then refer to the ngAnimate module into your application or add the ngAnimate as a dependency inside your application module.
The transclusion in Angular allows you to shift the original children of a directive into a specific location within a new template. The ng directive indicates the insertion point for a transcluded DOM of the nearest parent directive that is using transclusion. Attribute directives like ng-transclude or ng-transclude-slot are mainly used for transclusion.
Each angular application consist of one root scope but may have several child scopes. As child controllers and some directives create new child scopes, application can have multiple scopes. When new scopes are formed or created they are added as a children of their parent scope. Similar to DOM, they also creates a hierarchical structure.
When the page is loaded in the browser, following things happen:
Model View Controller or MVC as it is popularly called, is a software design pattern for developing web applications. A Model View Controller pattern is made up of the following three parts:
Yes! In AngularJS we can create custom directive to extend AngularJS existing functionalities.
Custom directives are used in AngularJS to extend the functionality of HTML. Custom directives are defined using "directive" function. A custom directive simply replaces the element for which it is activated. AngularJS application during bootstrap finds the matching elements and do one time activity using its compile() method of the custom directive then process the element using link() method of the custom directive based on the scope of the directive.
ngRoute is a module developed by angularJS team which was a part of the core angularJS framework. Whereas ui-router was developed by a third-party community to overcome the problems of ngRoute.
ngRoute is a location or URL based routing, and ui-router is a state-based routing which allows nested views.
ng-bind directive has one way data bindings, data flows only from object to UI, not vice versa (i.e. $scope>>view) and ng-model directive has two way data bindings, data flows between UI to object and vice versa(i.e. $scope>>view and view>>$scope).
Factories are functions that return the object, while services are constructor functions of the object which is used by a new keyword.
Syntax:
Factory – module.factory(`factoryName`, function);
Service – module.service(`serviceName`, function);
Event handling in AngularJs is very useful when you want to create advance AngularJs applications.
We need to handle DOM events like mouse clicks, moves, keyboard presses, change events and so on. AngularJs has some listener directives like ng-click, ng-dbl-click, ng-mousedown, ng-keydown, ng-keyup etc.
It is quite similar to service, factories implement a module pattern in which we use a factory method to generate an object which is used for building models.
In a factory, a method object is returned at the end by creating a new object and adding functions as properties.
Syntax:
module.factory(‘factoryName', function);
It is a web application which loads a single HTML page and dynamically updates the page as the user connects with the app.
By using AJAX and HTML a fluid and responsive web app can be created by SPA without invariant page reloads. Through this, we can make responsive UI with no page flicker.
In Angular, the digest process is known as dirty checking. It is called so as it scans the entire scope for changes. In other words, it compares all the new scope model values with the previous scope values. Since all the watched variables are contained in a single loop, any change/update in any of the variable leads to reassigning of rest of the watched variables present inside the DOM. A watched variable is in a single loop(digest cycle), any value change of any variable forces to reassign values of other watched variables in DOM
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