AngularJS (also known as Angular 1) is a discontinued
free and open-source
Free and open-source software (FOSS) is software available under a Software license, license that grants users the right to use, modify, and distribute the software modified or not to everyone free of charge. FOSS is an inclusive umbrella term ...
JavaScript
JavaScript (), often abbreviated as JS, is a programming language and core technology of the World Wide Web, alongside HTML and CSS. Ninety-nine percent of websites use JavaScript on the client side for webpage behavior.
Web browsers have ...
-based
web framework
A web framework (WF) or web application framework (WAF) is a software framework that is designed to support the development of web applications including web services, web resources, and web APIs. Web frameworks provide a standard way to build a ...
Google
Google LLC (, ) is an American multinational corporation and technology company focusing on online advertising, search engine technology, cloud computing, computer software, quantum computing, e-commerce, consumer electronics, and artificial ...
and a community of individuals and corporations. It aimed to simplify both the development and the testing of such applications by providing a framework for client-side
model–view–controller
Model–view–controller (MVC) is a software architectural pattern commonly used for developing user interfaces that divides the related program logic into three interconnected elements. These elements are:
* the model, the internal representat ...
(MVC) and model–view–viewmodel (MVVM) architectures, along with components commonly used in
web application
A web application (or web app) is application software that is created with web technologies and runs via a web browser. Web applications emerged during the late 1990s and allowed for the server to dynamically build a response to the request, ...
MEAN
A mean is a quantity representing the "center" of a collection of numbers and is intermediate to the extreme values of the set of numbers. There are several kinds of means (or "measures of central tendency") in mathematics, especially in statist ...
stack, that consisted of MongoDB database, Express.js web application server framework, AngularJS itself (or Angular), and Node.js server runtime environment.
As of January 1, 2022, Google no longer updates AngularJS to fix security, browser compatibility, or jQuery issues. The Angular team recommends upgrading to Angular (v2+) as the best path forward, but they also provided some other options.
Overview
The AngularJS framework worked by first reading the
HyperText Markup Language
Hypertext Markup Language (HTML) is the standard markup language for documents designed to be displayed in a web browser. It defines the content and structure of web content. It is often assisted by technologies such as Cascading Style Sheet ...
(HTML) page, which had additional custom
HTML attribute
HTML attributes are special words used to adjust the behavior or display of an ''HTML element''. An attribute either modifies the default functionality of an element type or provides functionality to certain element types unable to function corre ...
s embedded into it. Angular interpreted those attributes as directives to bind input or output parts of the page to a model that is represented by standard JavaScript variables. The values of those JavaScript variables could be manually set within the code or retrieved from static or dynamic
JSON
JSON (JavaScript Object Notation, pronounced or ) is an open standard file format and electronic data interchange, data interchange format that uses Human-readable medium and data, human-readable text to store and transmit data objects consi ...
resources.
AngularJS was built on the belief that
declarative programming
In computer science, declarative programming is a programming paradigm—a style of building the structure and elements of computer programs—that expresses the logic of a computation without describing its control flow.
Many languages that ap ...
should be used to create
user interface
In the industrial design field of human–computer interaction, a user interface (UI) is the space where interactions between humans and machines occur. The goal of this interaction is to allow effective operation and control of the machine fro ...
s and connect
software component
A software component is a modular unit of software that encapsulates specific functionality. The desired characteristics of a component are reusability and maintainability.
Value
Components allow software development to assemble software ...
s, while
imperative programming
In computer science, imperative programming is a programming paradigm of software that uses Statement (computer science), statements that change a program's state (computer science), state. In much the same way that the imperative mood in natural ...
was better suited to defining an application's
business logic
In computer software, business logic or domain logic is the part of the program that encodes the real-world business rules that determine how data can be created, stored, and changed. It is contrasted with the remainder of the software that might ...
. The framework adapted and extended traditional HTML to present dynamic content through two-way data-binding that allowed for the automatic synchronization of models and views. As a result, AngularJS de-emphasized explicit
Document Object Model
The Document Object Model (DOM) is a cros s-platform and language-independent API that treats an HTML or XML document as a tree structure wherein each node is an object representing a part of the document. The DOM represents a document with ...
(DOM) manipulation with the goal of improving testability and performance.
AngularJS's design goals included:
* to decouple DOM manipulation from application logic. The difficulty of this is dramatically affected by the way the code is structured.
* to decouple the client side of an application from the server-side. This allows development work to progress in parallel and allows for reuse of both sides.
* to provide structure for the journey of building an application: from designing the UI, through writing the business logic, to testing.
AngularJS implemented the MVC pattern to separate presentation, data, and logic components. Using dependency injection, Angular brought traditionally server-side services, such as view-dependent controllers, to client-side web applications. Consequently, much of the burden on the server could be reduced.
Scope
AngularJS used the term "scope" in a manner akin to the fundamentals of computer science.
Scope in computer science describes when in the program a particular binding is valid. The ECMA-262 specification defines scope as: a lexical environment in which a Function object is executed in client-side web scripts; akin to how scope is defined in
lambda calculus
In mathematical logic, the lambda calculus (also written as ''λ''-calculus) is a formal system for expressing computability, computation based on function Abstraction (computer science), abstraction and function application, application using var ...
.
As a part of the "MVC" architecture, the scope forms the "Model", and all variables defined in the scope can be accessed by the "View" as well as the "Controller". The scope behaves as a glue and binds the "View" and the "Controller".
Bootstrap
The task performed by the AngularJS bootstrapper occurred in three phases after the DOM has been loaded:
# Creation of a new Injector
# Compilation of the directives that decorate the DOM
# Linking of all directives to scope
AngularJS directives allowed the developer to specify custom and reusable HTML-like elements and attributes that define data bindings and the behavior of presentation components. Some of the most commonly used directives were:
;ng-animate: A module provides support for JavaScript, CSS3 transition and CSS3 keyframe animation hooks within existing core and custom directives.
;ng-app: Declares the root element of an AngularJS application, under which directives can be used to declare bindings and define behavior.
;ng-aria: A module for accessibility support of common ARIA attributes.
;ng-bind: Sets the text of a DOM element to the value of an expression. For example, displays the value of 'name' inside the span element. Any change to the variable 'name' in the application's scope reflect instantly in the DOM.
;ng-class: Conditionally apply a class, depending on the value of a Boolean expression.
;ng-controller: Specifies a JavaScript controller class that evaluates HTML expressions.
;ng-if: Basic if statement directive that instantiates the following element if the conditions are true. When the condition is false, the element is removed from the DOM. When true, a clone of the compiled element is re-inserted.
;ng-init: Called once when the element is initialized.
;ng-model: Similar to ng-bind, but establishes a two-way data binding between the view and the scope.
;ng-model-options: Provides tuning for how model updates are done.
;ng-repeat: Instantiate an element once per item from a collection.
;ng-show & ng-hide: Conditionally show or hide an element, depending on the value of a Boolean expression. Show and hide is achieved by setting the CSS display style.
;ng-switch: Conditionally instantiate one template from a set of choices, depending on the value of a selection expression.
;ng-view: The base directive responsible for handling routes that resolve JSON before rendering templates driven by specified controllers.
Since ng-* attributes are not valid in HTML specifications, data-ng-* can also be used as a prefix. For example, both ng-app and data-ng-app are valid in AngularJS.
Two-way data binding
AngularJS two-way data binding had its most notable feature, largely relieving the server backend of templating responsibilities. Instead, templates were rendered in plain HTML according to data contained in a scope defined in the model. The $scope service in Angular detected changes to the model section and modified HTML expressions in the view via a controller. Likewise, any alterations to the view were reflected in the model. This circumvented the need to actively manipulate the DOM and encouraged bootstrapping and rapid prototyping of web applications.
AngularJS detected changes in models by comparing the current values with values stored earlier in a process of dirty-checking, unlike Ember.js and Backbone.js that triggered listeners when the model values are changed.
;$watch
: is an angular method used for dirty checking. Any variable or expression assigned in $scope automatically sets up a in angular. So assigning a variable to or using directives like etc. all create watches in angular scope automatically. Angular maintains a simple array of in the objects
:Different ways of defining a watcher in AngularJS.
:* explicitly $watch an attribute on .
:*: $scope.$watch('person.username', validateUnique);
:* place an interpolation in your template (a watcher will be created for you on the current $scope).
:* ask a directive such as to define the watcher for you.
:*:
; $digest
: is angular method that is invoked internally by angularjs in frequent intervals. In method, angular iterates over all in its scope/child scopes.
;$apply
: is an angular method that internally invokes . This method is used when you want to tell angular manually start dirty checking (execute all )
;$destroy
: is both a method and event in angularjs. method, removes a scope and all its children from dirty checking. event is called by angular whenever a $scope or $controller is destroyed.
Development history
AngularJS was originally developed in 2009 by Miško Hevery at Brat Tech LLC as the software behind an online
JSON
JSON (JavaScript Object Notation, pronounced or ) is an open standard file format and electronic data interchange, data interchange format that uses Human-readable medium and data, human-readable text to store and transmit data objects consi ...
storage service, that would have been priced by the megabyte, for easy-to-make applications for the enterprise. This venture was located at the web domain "GetAngular.com", and had a few subscribers, before the two decided to abandon the business idea and release Angular as an open-source library.
The 1.6 release added many of the concepts of Angular to AngularJS, including the concept of a component-based application architecture. This release among others removed the Sandbox, which many developers believed provided additional security, despite numerous vulnerabilities that had been discovered that bypassed the sandbox. The current (as of November 2023) stable release of AngularJS is 1.8.3
In January 2018, a schedule was announced for phasing-out AngularJS: after releasing 1.7.0, the active development on AngularJS would continue until June 30, 2018. Afterwards, 1.7 was supported until December 31, 2021 as long-term support.
Legacy browser support
Versions 1.3 and later of AngularJS did not support Internet Explorer 8 or earlier. While AngularJS 1.2 supported IE8, its team does not.
Angular and AngularDart
Subsequent versions of AngularJS are simply called Angular. Angular is an incompatible
TypeScript
TypeScript (abbreviated as TS) is a high-level programming language that adds static typing with optional type annotations to JavaScript. It is designed for developing large applications and transpiles to JavaScript. It is developed by Micr ...
-based rewrite of AngularJS. Angular 4 was announced on 13 December 2016, skipping 3 to avoid a confusion due to the misalignment of the router package's version which was already distributed as v3.3.0.
AngularDart works on Dart, which is an object-oriented, class defined, single inheritance programming language using C style
syntax
In linguistics, syntax ( ) is the study of how words and morphemes combine to form larger units such as phrases and sentences. Central concerns of syntax include word order, grammatical relations, hierarchical sentence structure (constituenc ...
, that is different from Angular JS (which uses
JavaScript
JavaScript (), often abbreviated as JS, is a programming language and core technology of the World Wide Web, alongside HTML and CSS. Ninety-nine percent of websites use JavaScript on the client side for webpage behavior.
Web browsers have ...
) and Angular 2/ Angular 4 (which uses
TypeScript
TypeScript (abbreviated as TS) is a high-level programming language that adds static typing with optional type annotations to JavaScript. It is designed for developing large applications and transpiles to JavaScript. It is developed by Micr ...
). Angular 4 released in March 2017, with the framework's version aligned with the version number of the router it used. Angular 5 was released on November 1, 2017. Key improvements in Angular 5 include support for progressive Web apps, a build optimizer and improvements related to Material Design. Angular 6 was released on 3 May 2018, Angular 7 was released on 18 October 2018, and Angular 8 was released on May 28, 2019.
Angular follows Semantic Versioning standards, with each major version number indicating potentially breaking changes. Angular has pledged to provide 6 months of active support for each major version followed by 12 months of long-term support. Major releases are bi-yearly with 1 to 3 minor releases for every major release.
Angular Universal
A normal Angular application executes in the browser, while Angular Universal generates static application pages on the server through server-side rendering (SSR).
Libraries
AngularJS Material
AngularJS Material was a UI component library that implemented
Material Design
Material Design (codename Quantum Paper) is a design language developed by Google in 2014. Expanding on the "cards" UI that debuted in Google Now, Material Design uses more grid-based layouts, responsive animations and transitions, padding, an ...
in AngularJS. The library provided a set of reusable, well-tested, and accessible UI components. In January 2022, the library was closed, as announced on their official website. The AngularJS Material library is a mature and stable product that is ready for production use and works only with AngularJS 1.x. The Angular Material library is available in the angular/material GitHub repository
Chrome extension
In July 2012, the Angular team built an extension for the
Google Chrome
Google Chrome is a web browser developed by Google. It was first released in 2008 for Microsoft Windows, built with free software components from Apple WebKit and Mozilla Firefox. Versions were later released for Linux, macOS, iOS, iPadOS, an ...
browser called Batarang, that improved the debugging experience for web applications built with Angular. The extension aimed to allow for easy detection of performance bottlenecks and offered a GUI for debugging applications. For a time during late 2014 and early 2015, the extension was not compatible with recent releases (after v1.2.x) of Angular. The last update made to this extension was on April 4, 2017. Additionally, the extension was removed from the Chrome Web Store on June 1, 2022, due to its lack of updates and potential security concerns, such as requiring sensitive permissions.
Performance
AngularJS set out the paradigm of a ''digest cycle''. This cycle could be considered a loop, during which AngularJS checked if there were any changes to all the variables watched by all the $scopes. If $scope.myVar is defined in a controller and this variable was marked for watching, Angular would monitor the changes on myVar in each loop iteration.
This approach potentially led to slow rendering when AngularJS checked on too many variables in the $scope every cycle. Miško Hevery suggested keeping fewer than 2000 watchers on any page.
TypeScript
TypeScript (abbreviated as TS) is a high-level programming language that adds static typing with optional type annotations to JavaScript. It is designed for developing large applications and transpiles to JavaScript. It is developed by Micr ...