Web Front-end Performance Optimization Applications

With the rapid development of computer technology and network communication technology, the web applications become more and more popular. Web application is a necessary tool for everyone's life and services us in many fields-commerce, online entertainment and e-government are no longer new terms. The number of website grows sharply and the users increase in large scale. At the same time, its content and functionality has become very rich. In this case, the right Web site performance requirements have become more sophisticated, people not only want to see the contents they need, but also requires that their requests must be responsed as quickly as possible. The user can not stand waiting a long time in front of the browser. Therefore, web site optimization is imperative.Back-end optimization technology is relatively mature, such as database optimization, optimization of code-behind. But for Web front-end performance optimization, the research and attention are still far from enough. The majority of the sites are not concerned about the front-side optimization interiorly and researches in this area are few. In fact, the room of fornt-end optimization is very large. This thesis focuses on Web front-end optimization.My purposal is optimize the site without changing the original structure, without changing the database and background code in order to achieve success at the smallest cost.This thesis introduces the research background of web front-end optimization and the research level of home and abroad. At the beginning of this thesis we analysis the various models of Website in the development process to determine the scope of the front end. It put forwards the contents of front-end optimization and necessary of front-end optimization.Next, we research variety of factors that affect the performance of front-end, including the HTTP protocol, browser, caching mechanism, page size, page structure, as well as Ajax and other front-end relevant theories. This thesis puts forward a variety of front-end optimization technologies and methods. And through the combination of theory and experiments, the correctness and feasibility of those methods are validated. This thesis pays a lot attention to resolve the 2-connection request issue. Ajax is increasingly popular and the asynchronous way of working makes the browser's 2-connection issue more and more prominent. In order to avoid this problem and improve the user experience, this paper designs and implements a priority request queue which priority upgrade based on waiting time. In this way all asynchronous requests are placed in right place of priority. Requests are managed and sent by the queue to prevent more than two concurrent server connections.Finally we realized a website called Information Security Assessment website, and we apply the methods discussed above to this site to prove that these optimization methods are correct and feasible.