JavaScript

Related publications (26)

Scala.js: Type-Directed Interoperability with Dynamically Typed Languages

Sébastien Jean R Doeraene

Interoperability between statically typed and dynamically typed languages is increasingly important, as can be witnessed by the many statically typed languages targeting JavaScript. Interoperating with both the object-oriented and functional features of JavaScript is essential, if only to manipulate the DOM, yet existing languages have very poor support for this. We present Scala.js, a dialect of Scala compiling to JavaScript. Its interoperability system is based on a powerful and intuitive framework for type-directed interoperability with dynamically typed languages. The framework combines facade types for JavaScript values; user-defined, implicit, type-directed cross-language conversions; and a Dynamic type building on facade types and implicit conversions. It accommodates both the functional and object-oriented features of Scala and JavaScript, and provides very natural interoperability between the two languages. It is expressive enough to represent the DOM and jQuery APIs, among others, both in its statically typed and dynamically typed flavors.

2013

Cross-Platform Language Design

Sébastien Jean R Doeraene

Programming languages are increasingly compiled to multiple runtimes, each featuring their own rich structures such as their object model. Furthermore, they need to interact with other languages targeting said runtimes. A language targeting only one runtime can be designed to tailor its semantics to those of that runtime, for easy interoperability with other languages. However, in a language targeting multiple runtimes with differing semantics, it is difficult to cater to each of them while retaining a common behavior across runtimes. We call \emph{cross-platform language} a language that aims at being both \emph{portable} across platforms and \emph{interoperable} with each target platform. Portability is the ability for a program or a library to cross-compile for multiple platforms, and behave the same way on all of them. Interoperability is the ability to communicate with other languages on the same platform. While many cross-compiling languages focus on one of these two properties---only adding support for the other one as an afterthought---, languages that are designed from the ground up to support both are rare. In this thesis, we present the design of Scala.js, the dialect of Scala targeting the JavaScript platform, which turned Scala into a cross-platform language. On the one hand, Scala programs can be cross-compiled for the JVM and JavaScript with portable semantics. On the other hand, whereas Scala/JVM interoperates with Java, Scala.js interoperates with JavaScript, allowing to use any JavaScript library. Along the dissertation, we give insights that can be transferred to the design of other cross-platform languages, although with a bias towards those targeting the JVM and JavaScript. The first and most obvious challenge is to reconcile the static nature of Scala's object model with JavaScript's dynamic one. Besides the ability to mutate a class hierarchy at run-time in JavaScript, there are fundamental differences between the two models, in particular the difference between compile-time overloading and run-time overloading. We discuss how such semantic mismatches can live in harmony within the language. The second challenge is to obtain good performance from a language where interoperability with a dynamic and unknown part of the program is pervasive. To that end, we design and specify an intermediate representation (IR) with first-class support for dynamically typed interoperability features in addition to statically typed JVM-style operations. Despite its tight integration with the open world of JavaScript, most of the IR can be considered as a closed world where advanced whole-program optimizations can be performed. The performance of the overall system is evaluated and shown to be competitive with hand-written JavaScript, and even with Scala/JVM in some cases.

EPFL2018

Cross-Platform Language Design in Scala.js (Keynote)

Sébastien Jean R Doeraene

Have you ever wondered what is the secret sauce of Scala.js? What defines Scala.js, above all else, is the overarching will to make it cross-platform. A cross-platform language is both portable-most source code cross-compiles and behaves the same way on multiple platforms-and interoperable-code written in that language can interoperate with other languages on the target platforms. Most multi-platform languages are designed with one of those two properties in mind, and only address the other one as an afterthought. This results in poor integration, difficulty to write portable code, or even the impossibility to use some platform-specific libraries. This talk shows how Scala.js was designed as a cross-platform language. We show how portability and interoperability drive every design decision, from which language feature to include to performance considerations. We state a criteria of completeness for interoperability, and show how Scala.js satisfies it (with the exception of one JavaScript language feature, still work-in-progress). We give insights about what features are critical for portability, and which ones can be relaxed in the name of performance. In particular, we stress the importance of the ecosystem of libraries: existing assumptions in the ecosystem can force the language designer into reproducing behaviors of Scala/JVM, even when they are accidental. As a practical exercise, we study the main language changes that made it into Scala.js 1.x wrt. 0.6.x-as well as possible future developments-and how they fit into the cross-platform language design methodology.

ASSOC COMPUTING MACHINERY2018

Semantics-Driven Interoperability between Scala.js and JavaScript

Sébastien Jean R Doeraene, Tobias Schlatter, Nicolas Alexander Stucki

Hundreds of programming languages compile to JavaScript. Yet, most of them fail, at one level or another, to provide satisfactory interoperability with JavaScript APIs. This is limiting, as interoperability is at least required to manipulate web pages through the DOM API, but also to use the ecosystem of existing JavaScript libraries. This paper presents the interoperability features of Scala.js, which solves the shortcomings of previous approaches. Scala. js offers a separate hierarchy of JavaScript types, whose operations have semantics borrowed from ECMAScript 2015. The interoperability features are complete with respect to ECMAScript 2015, save for two exceptions which are still being worked on. This allows Scala. js programs to perform any operation that an ECMAScript program could do, thereby guaranteeing that they can talk to any JavaScript library.

Association for Computing Machinery2016

JavaScript as an Embedded DSL

Nada Amin, Grzegorz Kossakowski, Martin Odersky, Tiark Rompf

Developing rich web applications requires mastering different environments on the client and server sides. While there is considerable choice on the server-side, the client-side is tied to JavaScript, which poses substantial software engineering challenges, such as moving or sharing pieces of code between the environments. We embed JavaScript as a DSL in Scala, using Lightweight Modular Staging. DSL code can be compiled to JavaScript or executed as part of the server application. We use features of the host language to make client-side programming safer and more convenient. We use gradual typing to interface typed DSL programs with existing JavaScript APIs. We exploit a selective CPS transform already available in the host language to provide a compelling abstraction over asynchronous callback-driven programming in our DSL.

Springer Berlin Heidelberg2012

Some Things You Always Wanted to Know About Web Pages (But Were Too Busy to Ask)

Simon Schubert, Willy Zwaenepoel

The organic growth of the web has led to web sites that exhibit a large variety of properties. We conduct a large- scale study to gain quantitative insights into the browser-side effects of the structure and behavior of thousands of the most popular web sites. We find that 50 % of web pages load more than 100 resources from more than 17 distinct hosts and make the browser process more than 730 kB of javascript. Embedded third-party advertisements are the prevailing model on the web to monetize services or content that are otherwise provided free-of-cost to end users. We quantify the effects on browser-side resource consumption caused by advertisements and find that on pages with ads, the ads make up 20 % of all HTTP requests. Furthermore, ads lead to three times as many javascript background events that prevent the processor from staying in deep sleep mode.

2012

Stepwise Refinement of Formal Specifications Based on Logical Formulae: from COOPN/2 Specifications to Java Programs

One of the steps making it possible to increase the quality and the reliability of the software executing on distributed systems consists of the use of methods of software engineering that are known as formal. The majority of the formal methods currently existing correspond in fact more to formal specifications languages than to methods themselves. This is due to the fact that the two fundamental aspects which are: the logic of use of the language and the coverage of the software life cycle are not, for the majority, defined. The development by stepwise refinement is one of the means making it possible to define these two aspects. This thesis aims to the definition of the concepts of refinement and implementation of model-oriented formal specifications. It brings a methodological base making it possible to use such a specifications language during a development by stepwise refinements and during the implementation stage. This thesis defines, initially, a theoretical framework for the refinement and the implementation of formal specifications. The main idea consists in associating a contract with each specification. A contract explicitly represents the whole of the properties of the specification which it is necessary to preserve at the time of a refinement of this specification. To show that a concrete specification refines some abstract specification, it is then a matter of showing that the contract of the concrete specification is sufficient to ensure the properties corresponding to the contract of the abstract specification. The second part of this thesis consists in applying this theoretical framework in the context of the CO-OPN/2 language. CO-OPN/2 is an object-oriented formal specifications language founded on algebraic specifications and Petri nets. Thus, definitions of the concepts of contracts, refinement and implementation are proposed for this language. The contracts are expressed using the Hennessy-Milner temporal logic (HML). This logic is used in the theory of test provided with language CO-OPN/2. Thus, the verification of the contractual properties, as well as the verification of the stages of refinement are facilitated. Refinement and implementation are controlled semantically by the satisfaction of the contracts; syntactically, a renaming is authorised. We specifically study the implementation using the Java programming language. We show how to specify classes of the Java programming language using language CO-OPN/2, so that the last stage of the process of refinement leads to a specification entirely built using CO-OPN/2 components specifying Java classes. The stage of implementation in the Java language itself is thus facilitated. The third part of this thesis shows how it is possible to practically verify that a CO-OPN/2 specification satisfies its own contract, that a stage of refinement is correctly carried out, and finally that the stage of implementation is correctly performed. These verifications are carried out using the theory of the test provided with language CO-OPN/2. Finally, the last part of this thesis illustrates the cogency of this approach by applying it to a complete and detailed case study. A distributed Java application is developped according to the method introduced for the CO-OPN/2 language. Refinement is guided mainly by the satisfaction of functional requirements and by constraints of design integrating the concept of client/server architecture. Lastly, the stages chosen in the refinement process of this development make it possible to study aspects specific to distributed applications, and to propose generic schemas for the design of such applications.

1999

Formal Development of Java Programs

The Java object-oriented programming language has been the subject of an important involvement from programmers and industry. Especially for applications related to the Web. The problem of such rapid penetration of Java programs into commercial product is that software engineers does not have any methodology and have to develop complex parallel applications. In this paper, we present, using a real (http://lglsun.epfl.ch/Team/GDM/DSGamma.html) but simple Web parallel application, a possible formal development methodology based on the stepwise refinement of CO-OPN/2 formal specifications. The application chosen is based on the Gamma paradigm, in which additions are realized across distributed multisets of integers maintained by local Java applets. CO-OPN/2 is an object-oriented specification formalism allowing the formal specification of abstract data types based on algebraic specification and of concurrent objects using a Petri net like approach. An interesting feature of CO-OPN/2 is that it gives a coherent solution for the expression of complex properties combining inheritance, concurrency and synchronizations. The refinement of formal descriptions for building progressively the Java program is presented in several refinement steps. This refinement process focuses on the distribution of data and treatments, and validation and verification are studied through the refinement of system properties.

1997

Formal Development of Java Based Web Parallel Applications

The Java object-oriented programming language has been the subject of an important involvement from programmers and the industry. Especially for applications related to the Web. The problem of such a rapid penetration of Java programs into commercial products is that software engineers do not have any methodology and have to develop complex parallel applications. Here, we present a formal development methodology based on the stepwise refinement of CO-OPN/2 formal specifications, using a real Web parallel application. Starting from a centralized view, we present the following refinement steps: data distribution, behavior distribution, communication layer, and Java program. During the whole refinement process, we study the evolution and the verification of one specific property.

1998

A principled approach to the design of collaborative MOOC curricula

Stian Haklev

MOOCs have the potential to benefit from the large number of very diverse learners that participate in courses, but this requires a principled approach to MOOC curriculum development. Courses need to take into consideration the diversity of learner experience and intentions, and incorporate scripts that both benefit from the large numbers of learners (crowd-sourcing), as well as enabling small-scale intense collaboration. The real challenge is tying together a set of learning activities and the development of a community knowledge base, with the specific curriculum learning goals of the course. This paper offers a pragmatic approach to developing courses, based on the experience of a MOOC for teacher professional development.

2017