File Name: spa design and architecture understanding single page web applications .zip
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 the browser loading entire new pages.
There are various techniques available that enable the browser to retain a single page even when the application requires server communication. Aside from ExtJS, all of these are open source. As of , the most prominent technique used was Ajax. Ajax has further been popularized by libraries like jQuery , which provides a simpler syntax and normalizes Ajax behavior across different browsers which historically had varying behavior.
WebSockets are a bidirectional real-time client-server communication technology that are part of the HTML5 specification. For real-time communication, their use is superior to Ajax in terms of performance  and simplicity. Server-sent events SSEs is a technique whereby servers can initiate data transmission to browser clients. Once an initial connection has been established, an event stream remains open until closed by the client. Although this method is outdated, asynchronous calls to the server may also be achieved using browser plug-in technologies such as Silverlight , Flash , or Java applets.
Requests to the server typically result in either raw data e. A SPA moves logic from the server to the client, with the role of the web server evolving into a pure data API or web service. This architectural shift has, in some circles, been coined "Thin Server Architecture" to highlight that complexity has been moved from the server to the client, with the argument that this ultimately reduces overall complexity of the system.
The server keeps the necessary state in memory of the client state of the page. At the same time, the state in server is updated. Most of the logic is executed on the server, and HTML is usually also rendered on the server.
This approach requires that more data be sent to the server and may require more computational resources per request to partially or fully reconstruct the client page state in the server. At the same time, this approach is more easily scalable because there is no per-client page data kept in the server and, therefore, Ajax requests can be dispatched to different server nodes with no need for session data sharing or server affinity.
They also break HTTP referer headers as browsers are not allowed to send the fragment identifier in the Referer header. Alternatively, applications may render the first page load on the server and subsequent page updates on the client. This is traditionally difficult, because the rendering code might need to be written in a different language or framework on the server and in the client. Using logic-less templates, cross-compiling from one language to another, or using the same language on the server and the client may help to increase the amount of code that can be shared.
Use cases include applications that surface private data hidden behind an authentication system. In the cases where these applications are consumer products, often a classic "page redraw" model is used for the applications landing page and marketing site, which provides enough meta data for the application to appear as a hit in a search engine query. Blogs, support forums, and other traditional page redraw artifacts often sit around the SPA that can seed search engines with relevant terms.
As of version 1. Another possible choice is frameworks like PreRender, Puppeteer, Rendertron which can be easily integrated into any website as a middleware with web server configuration enabling bot requests google bot and others to be served by the middleware while non-bot requests are served as usual.
These frameworks cache the relevant website pages periodically to allow latest versions be available to search engines. These frameworks have been officially approved by google. There are a couple of workarounds to make it look as though the web site is crawlable. Both of these do require quite a bit of effort, and can end up giving a maintenance headache for the large complex sites. There are also potential SEO pitfalls.
Running PhantomJS to output the HTML can slow down the response speed of the pages, which is something for which search engines — Google in particular — downgrade the rankings. One way to increase the amount of code that can be shared between servers and clients is to use a logic-less template language like Mustache or Handlebars.
To avoid these problems, applications can use UI data bindings or granular DOM manipulation to only update the appropriate parts of the page instead of re-rendering entire templates. With a SPA being, by definition, "a single page", the model breaks the browser's design for page history navigation using the "forward" or "back" buttons. This presents a usability impediment when a user presses the back button, expecting the previous screen state within the SPA, but instead, the application's single page unloads and the previous page in the browser's history is presented.
As long as the SPA is capable of resurrecting the same screen state from information contained within the URL hash, the expected back-button behavior is retained. Analytics tools such as Google Analytics rely heavily upon entire new pages loading in the browser, initiated by a new page load. SPAs do not work this way. After the first page load, all subsequent page and content changes are handled internally by the application, which should simply call a function to update the analytics package.
Failing to call said function, the browser never triggers a new page load, nothing gets added to the browser history, and the analytics package has no idea who is doing what on the site. The difficulty comes in managing this and ensuring that everything is being tracked accurately — this involves checking for missing reports and double entries.
Some frameworks provide open source analytics integrations addressing most of the major analytics providers. Developers can integrate them into the application and make sure that everything is working correctly, but there is no need to do everything from scratch. Single-Page Applications have a slower first page load than server-based applications. This is because the first load has to bring down the framework and the application code before rendering the required view as HTML in the browser.
A server-based application just has to push out the required HTML to the browser, reducing the latency and download time. There are some ways of speeding up the initial load of a SPA, such as a heavy approach to caching and lazy-loading modules when needed.
But it's not possible to get away from the fact that it needs to download the framework, at least some of the application code, and will most likely hit an API for data before displaying something in the browser. The question of performance and wait-times remains a decision that the developer must make.
A SPA is fully loaded in the initial page load and then page regions are replaced or updated with new page fragments loaded from the server on demand. To avoid excessive downloading of unused features, a SPA will often progressively download more features as they become required, either small fragments of the page, or complete screen modules. In this way an analogy exists between "states" in a SPA and "pages" in a traditional website. Because "state navigation" in the same page is analogous to page navigation, in theory, any page-based web site could be converted to single-page replacing in the same page only the changed parts.
The SPA approach on the web is similar to the single-document interface SDI presentation technique popular in native desktop applications. From Wikipedia, the free encyclopedia. Web application that interacts with the user by dynamically rewriting a web page.
This section needs additional citations for verification. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. Falafel Software Blog. Retrieved January 18, Retrieved February 3, Retrieved July 6, Retrieved April 12, Meteor Blaze is a powerful library for creating live-updating user interfaces.
We built it because we thought that other libraries made user interface programming unnecessarily difficult and confusing. Archived from the original on March 20, Retrieved January 31,
SPA Design and Architecture
However, in the past SPAs have left marketers out in the dark when it comes to managing content. The SPA only sends what you need with each click, and your browser renders that information. This is different to a traditional page load where the server re-renders a full page with every click you make and sends it to your browser. This piece by piece, client side method makes load time must faster for users and makes the amount of information a server has to send a lot less and a lot more cost efficient. A win-win. This approach voids interruption of the user experience between successive pages, making the application behave more like a desktop application.
Skip to content. All Homes Search Contact. When you start to work on a Spa Design project with Spa Design and Architecture Consultants, we will take you through a very detailed step by step process. This presents a usability impediment when a user presses the back button, expecting the previous screen state within the SPA, but instead, the application's single page unloads and the previous page in the browser's history is presented. Interior design B. It starts with an introduction to the SPA model and builds on the standard approach of creating linked pages. It gives an awesome fragrance and look.
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This book is full of easy-to-follow examples you can apply to the library or framework of your choice. The next step in the development of web-based software, single-page web applications deliver the sleekness and fluidity of a native desktop application in a browser. Emmit Scott is a senior software engineer and architect with experience building large-scale, web-based applications.
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