A virtual DOM is a lightweight JavaScript representation of the Document Object Model (DOM) used in declarative web frameworks such as React, Vue.js, and Elm. [1] Since generating a virtual DOM is relatively fast, any given framework is free to rerender the virtual DOM as many times as needed relatively cheaply. The framework can then find the differences between the previous virtual DOM and the current one (diffing), and only makes the necessary changes to the actual DOM (reconciliation). [2] [3] While technically slower than using just vanilla JavaScript, the pattern makes it much easier to write websites with a lot of dynamic content, since markup is directly coupled with state.
Similar techniques include Ember.js' Glimmer and Angular's incremental DOM. [4] [5]
The JavaScript DOM API has historically been inconsistent across browsers, clunky to use, and difficult to scale for large projects. While libraries like jQuery aimed to improve the overall consistency and ergonomics of interacting with HTML, [6] it too was prone to repetitive code that didn't describe the nature of the changes being made well and decoupled logic from markup.
The release of AngularJS in 2010 provided a major paradigm shift in the interaction between JavaScript and HTML with the idea of dirty checking. [7] Instead of imperatively declaring and destroying event listeners and modifying individual DOM nodes, changes in variables were tracked and sections of the DOM were invalidated and rerendered when a variable in their scope changed. This digest cycle provided a framework to write more declarative code that coupled logic and markup in a more logical way.
While AngularJS aimed to provide a more declarative experience, it still required data to be explicitly bound to and watched by the DOM, and performance concerns were cited over the expensive process of dirty checking hundreds of variables. [8] To alleviate these issues, React was the first major library to adopt a virtual DOM in 2013, which removed both the performance bottlenecks (since diffing and reconciling the DOM was relatively cheap) and the difficulty of binding data (since components were effectively just objects). [9] Other benefits of a virtual DOM included improved security since XSS was effectively impossible and better extensibility since a component's state was entirely encapsulated. [10] Its release also came with the advent of JSX, which further coupled HTML and JavaScript with an XML-like syntax extension.
Following React's success, many other web frameworks copied the general idea of an ideal DOM representation in memory, such as Vue.js in 2014, which used a template compiler instead of JSX and had fine-grained reactivity built as part of the framework. [11]
In recent times, the virtual DOM has been criticized for being slow due to the additional time required for diffing and reconciling DOM nodes. [12] This has led to the development of frameworks without a virtual DOM, such as Svelte, and frameworks that edit the DOM in-place such as Angular 2.
React pioneered the use of a virtual DOM to make components declaratively. Virtual DOM nodes are constructed using the createElement()
function, but are often transpiled from JSX to make writing components more ergonomic. [13] In class-based React, virtual DOM nodes are returned from the render()
function, while in functional hook-based components, the return value of the function itself serves as the page markup.
Vue.js uses a virtual DOM to handle state changes, but is usually not directly interacted with; instead, a compiler is used to transform HTML templates into virtual DOM nodes as an implementation detail. [14] While Vue supports writing JSX and custom render functions, [15] it's more typical to use the template compiler since a build step isn't required that way.
Svelte does not have a virtual DOM, with its creator Rich Harris calling the virtual DOM "pure overhead". [16] Instead of diffing and reconciling DOM nodes at runtime, Svelte uses compile-time reactivity to analyze markup and generate JavaScript code that directly edits the HTML, drastically increasing performance. [17]
The Document Object Model (DOM) is a cross-platform and language-independent interface 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 a logical tree. Each branch of the tree ends in a node, and each node contains objects. DOM methods allow programmatic access to the tree; with them one can change the structure, style or content of a document. Nodes can have event handlers attached to them. Once an event is triggered, the event handlers get executed.
Web development is the work involved in developing a website for the Internet or an intranet. Web development can range from developing a simple single static page of plain text to complex web applications, electronic businesses, and social network services. A more comprehensive list of tasks to which Web development commonly refers, may include Web engineering, Web design, Web content development, client liaison, client-side/server-side scripting, Web server and network security configuration, and e-commerce development.
In computing, a solution stack or software stack is a set of software subsystems or components needed to create a complete platform such that no additional software is needed to support applications. Applications are said to "run on" or "run on top of" the resulting platform.
Svelte is a free and open-source component-based front-end software framework, and language created by Rich Harris and maintained by the Svelte core team members.
A single-page application (SPA) is a web application or website that interacts with the user by dynamically rewriting the current web page with new data from the web server, instead of the default method of loading entire new pages. The goal is faster transitions that make the website feel more like a native app.
Model–view–viewmodel (MVVM) is an architectural pattern in computer software that facilitates the separation of the development of a graphical user interface —be it via a markup language or GUI code—from the development of the business logic or back-end logic such that the view is not dependent upon any specific model platform.
AngularJS is a discontinued free and open-source JavaScript-based web framework for developing single-page applications. It was maintained mainly by Google 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 (MVC) and model–view–viewmodel (MVVM) architectures, along with components commonly used in web applications and progressive web applications.
Elm is a domain-specific programming language for declaratively creating web browser-based graphical user interfaces. Elm is purely functional, and is developed with emphasis on usability, performance, and robustness. It advertises "no runtime exceptions in practice", made possible by the Elm compiler's static type checking.
JavaScript templating refers to the client side data binding method implemented with the JavaScript language. This approach became popular thanks to JavaScript's increased use, its increase in client processing capabilities, and the trend to outsource computations to the client's web browser. Popular JavaScript templating libraries are AngularJS, Backbone.js, Ember.js, Handlebars.js, JSX, Vue.js and Mustache.js. A frequent practice is to use double curly brackets to call values of the given key from data files, often JSON objects.
Meteor, or MeteorJS, is a partly proprietary, mostly free and open-source isomorphic JavaScript web framework written using Node.js. Meteor allows for rapid prototyping and produces cross-platform code. The server-side MongoDB program is the only proprietary component of Meteor and is part of the Meteor download bundle. It is possible to use Meteor without using the server-side MongoDB. It uses the Distributed Data Protocol and a publish–subscribe pattern to automatically propagate data changes to clients without requiring the developer to write any synchronization code. On the client, Meteor can be used with any popular front-end JS framework, Vue, React, Svelte, Angular, or Bazel.
React is a free and open-source front-end JavaScript library that aims to make building user interfaces based on components more "seamless". It is maintained by Meta and a community of individual developers and companies.
Ionic is an open-source UI toolkit for building cross-platform mobile, web, and desktop applications using web technologies such as HTML, CSS, and JavaScript/TypeScript. It provides a set of pre-designed UI components and tools for building high-quality, interactive applications. Ionic was originally built as a complete open-source SDK for hybrid mobile app development created by Max Lynch, Ben Sperry, and Adam Bradley of Drifty Co. in 2013. The original version was released in 2013 and built on top of AngularJS and Apache Cordova. However, the latest release was re-built as a set of Web Components using StencilJS, allowing the user to choose any user interface framework, such as Angular, React or Vue.js. It also allows the use of Ionic components with no user interface framework at all. Ionic provides tools and services for developing hybrid mobile, desktop, and progressive web apps based on modern web development technologies and practices, using Web technologies like CSS, HTML5, and Sass. In particular, mobile apps can be built with these Web technologies and then distributed through native app stores to be installed on devices by utilizing Cordova or Capacitor.
React Native is an open-source UI software framework developed by Meta Platforms. It is used to develop applications for Android, Android TV, iOS, macOS, tvOS, Web, Windows and UWP by enabling developers to use the React framework along with native platform capabilities. It is used to develop Android and iOS applications at Facebook, Microsoft, and Shopify. It is also being used to develop virtual reality applications at Oculus.
Vue.js is an open-source model–view–viewmodel front end JavaScript framework for building user interfaces and single-page applications. It was created by Evan You and is maintained by him and the rest of the active core team members.
Angular is a TypeScript-based free and open-source single-page web application framework. It is developed by Google and by a community of individuals and corporations. Angular is a complete rewrite from the same team that built AngularJS. The Angular ecosystem consists of a diverse group of over 1.7 million developers, library authors, and content creators. According to the Stack Overflow Developer Survey, Angular is one of the most commonly used web frameworks.
This is a list of articles related to the JavaScript programming language.
ESLint is a static code analysis tool for identifying problematic patterns found in JavaScript code. It was created by Nicholas C. Zakas in 2013. Rules in ESLint are configurable, and customized rules can be defined and loaded. ESLint covers both code quality and coding style issues. ESLint supports current standards of ECMAScript, and experimental syntax from drafts for future standards. Code using JSX or TypeScript can also be processed when a plugin or transpiler is used.
Next.js is an open-source web development framework created by the private company Vercel providing React-based web applications with server-side rendering and static rendering.
In web development, hydration or rehydration is a technique in which client-side JavaScript converts a web page that is static from the perspective of the web browser, delivered either through static rendering or server-side rendering, into a dynamic web page by attaching event handlers to the HTML elements in the DOM. Because the HTML is pre-rendered on a server, this allows for a fast "first contentful paint", but there is a period of time afterward where the page appears to be fully loaded and interactive, but is not until the client-side JavaScript is executed and event handlers have been attached.
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