<p>In the last decade, web browsers have seen a remarkable increase of performance, especially in the JavaScript engines. JavaScript has over the years gone from being a slow and rather limited language, to today have become feature-rich and fast. It’s speed can be around the same or half of comparable code written in C++, but this speed is directly dependent on the choice of the web browser, and the best performance is seen in browsers using JIT compilation techniques.</p><p>Even though the language has seen a dramatic increase in performance, there’s still major problems regarding memory usage. JavaScript applications typically consume 3-4 times more memory than similar applications written in C++. Many browser vendors, like Opera Software, acknowledge this and are currently trying to optimize their memory usage. This issue is hopefully non-existent within a near future.</p><p>Because the majority of scientific papers written about JavaScript only compare performance using the industry benchmarks SunSpider and V8, this thesis have chosen to widen the scope. The benchmarks really give no information about how JavaScript stands in comparison to C#, C++ and other popular languages. To be able to compare that, I’ve implemented a GIF decoder, an XML parser and various elementary tests in both JavaScript and C++ to compare how far apart the languages are in terms of speed, memory usage and responsiveness.</p>

<p>Under 1990-talet utspelade sig en bitter kamp om marknadsandelar mellan de två ledande webbläsare Internet Explorer och Netscape Navigator, det så kallade webbläsar-kriget. Kriget hade till följd att webbläsarna blev nästan helt inkompatibla. Sedan dess pågår en ständig utveckling av gemensamma standarder för webben. Idag är förutsättningarna för kompatibilitet mycket bättre än för tio år sidan, men problemet är inte fullständigt avhjälpt. De moderna webbläsare Internet Explorer 6, Firefox 1.5, Opera 8.5 och Safari kan återge en och samma webbsida visas på olika sätt trots att det finns gemensamma standarder. Syftet med denna uppsats är att ta reda på de tekniska orsakerna bakom problemet samt att ta fram lösningsförslag för att skapa en webbsida som är helt kompatibel i de moderna webbläsarna. Uppsatsen innehåller ett omfattande teorikapitel som behandlar definitioner, historik och problem. Teorin kompletteras av tre fältintervjuer med professionella webbutvecklare. Undersökningarna visar att kompati-bilitetsproblem beror på flera faktorer och att det är omöjligt att skapa en heltäckande lösning som kommer åt alla problem. Men genom att kombinera olika tekniker kan man skapa en metod som täcker en stor del av såväl generella som specifika kompatibilitetsproblemen utan att kollidera med rekommenderade standarder.</p> / <p>During the 1990’s the two leading web browsers, Internet Explorer and Netscape Navigator, fought each other in a battle for market shares, the so-called browser war. This war caused almost complete incompatibility between the web browsers. Since then, there has been a continual development of common standards for the web. Today conditions for compatibility are a lot better compared to ten years ago, but the problem is not completely solved. The modern web browsers Internet Explorer 6, Firefox 1.5, Opera 8.5 and Safari can display the exact same web page differently despite common standards. The aim of this essay is to investigate the technical causes of the problem and to develop suggested solutions for creating a web page that is fully compatible in modern browsers. The essay contains an extensive literature study, considering definitions, history and problems. The theory was completed with three field interviews with professional web designers. The investigations show that compatibility problems depend on several factors and that it is impossible to create one exhaustive solution that encompasses all problems. However, by combining different techniques one can create a method that covers a large part of both general and specific compatibility problems without colliding with recommended standards.</p>

In the last decade, web browsers have seen a remarkable increase of performance, especially in the JavaScript engines. JavaScript has over the years gone from being a slow and rather limited language, to today have become feature-rich and fast. It’s speed can be around the same or half of comparable code written in C++, but this speed is directly dependent on the choice of the web browser, and the best performance is seen in browsers using JIT compilation techniques. Even though the language has seen a dramatic increase in performance, there’s still major problems regarding memory usage. JavaScript applications typically consume 3-4 times more memory than similar applications written in C++. Many browser vendors, like Opera Software, acknowledge this and are currently trying to optimize their memory usage. This issue is hopefully non-existent within a near future. Because the majority of scientific papers written about JavaScript only compare performance using the industry benchmarks SunSpider and V8, this thesis have chosen to widen the scope. The benchmarks really give no information about how JavaScript stands in comparison to C#, C++ and other popular languages. To be able to compare that, I’ve implemented a GIF decoder, an XML parser and various elementary tests in both JavaScript and C++ to compare how far apart the languages are in terms of speed, memory usage and responsiveness.

Under 1990-talet utspelade sig en bitter kamp om marknadsandelar mellan de två ledande webbläsare Internet Explorer och Netscape Navigator, det så kallade webbläsar-kriget. Kriget hade till följd att webbläsarna blev nästan helt inkompatibla. Sedan dess pågår en ständig utveckling av gemensamma standarder för webben. Idag är förutsättningarna för kompatibilitet mycket bättre än för tio år sidan, men problemet är inte fullständigt avhjälpt. De moderna webbläsare Internet Explorer 6, Firefox 1.5, Opera 8.5 och Safari kan återge en och samma webbsida visas på olika sätt trots att det finns gemensamma standarder. Syftet med denna uppsats är att ta reda på de tekniska orsakerna bakom problemet samt att ta fram lösningsförslag för att skapa en webbsida som är helt kompatibel i de moderna webbläsarna. Uppsatsen innehåller ett omfattande teorikapitel som behandlar definitioner, historik och problem. Teorin kompletteras av tre fältintervjuer med professionella webbutvecklare. Undersökningarna visar att kompati-bilitetsproblem beror på flera faktorer och att det är omöjligt att skapa en heltäckande lösning som kommer åt alla problem. Men genom att kombinera olika tekniker kan man skapa en metod som täcker en stor del av såväl generella som specifika kompatibilitetsproblemen utan att kollidera med rekommenderade standarder. / During the 1990’s the two leading web browsers, Internet Explorer and Netscape Navigator, fought each other in a battle for market shares, the so-called browser war. This war caused almost complete incompatibility between the web browsers. Since then, there has been a continual development of common standards for the web. Today conditions for compatibility are a lot better compared to ten years ago, but the problem is not completely solved. The modern web browsers Internet Explorer 6, Firefox 1.5, Opera 8.5 and Safari can display the exact same web page differently despite common standards. The aim of this essay is to investigate the technical causes of the problem and to develop suggested solutions for creating a web page that is fully compatible in modern browsers. The essay contains an extensive literature study, considering definitions, history and problems. The theory was completed with three field interviews with professional web designers. The investigations show that compatibility problems depend on several factors and that it is impossible to create one exhaustive solution that encompasses all problems. However, by combining different techniques one can create a method that covers a large part of both general and specific compatibility problems without colliding with recommended standards.

In software development projects, bug triage consists mainly of assigning bug reports to software developers or teams (depending on the project). The partial or total automation of this task would have a positive economic impact on many software projects. This thesis introduces a systematic four-step method to find some of the best configurations of several machine learning algorithms intending to solve the automatic bug assignment problem. These four steps are respectively used to select a combination of pre-processing techniques, a bug report representation, a potential feature selection technique and to tune several classifiers. The aforementioned method has been applied on three software projects: 66 066 bug reports of a proprietary project, 24 450 bug reports of Eclipse JDT and 30 358 bug reports of Mozilla Firefox. 619 configurations have been applied and compared on each of these three projects. In production, using the approach introduced in this work on the bug reports of the proprietary project would have increased the accuracy by up to 16.64 percentage points.

The aim of the thesis was to design, implement and evaluate the results of automatic tests for the JavaScript Restrictor project, which is being developed as a web browser extension. The tests are divided into three levels - unit, integration, and system. The Unit Tests verify the behavior of individual features, the Integration Tests verify the correct wrapping of browser API endpoints, and the System Tests check that the extension does not suppress the desired functionality of web pages. The System Tests are implemented for parallel execution in a distributed environment which has succeeded in achieving an almost directly proportional reduction in time with respect to the number of the tested nodes. The benefit of this work is detection of previously unknown errors in the JavaScript Restrictor extension and provision of the necessary information that allowed to fix some of the detected bugs.