Putting in all the stops: execution control for JavaScript

Abstract

Scores of compilers produce JavaScript, enabling programmers to use many languages on the Web, reuse existing code, and even use Web IDEs. Unfortunately, most compilers inherit the browser's compromised execution model, so longrunning programs freeze the browser tab, infinite loops crash IDEs, and so on. The few compilers that avoid these problems suffer poor performance and are difficult to engineer. This paper presents Stopify, a source-to-source compiler that extends JavaScript with debugging abstractions and blocking operations, and easily integrates with existing compilers. We apply Stopify to ten programming languages and develop a Web IDE that supports stopping, single-stepping, breakpointing, and long-running computations. For nine languages, Stopify requires no or trivial compiler changes. For eight, our IDE is the first that provides these features. Two of our subject languages have compilers with similar features. Stopify's performance is competitive with these compilers and it makes them dramatically simpler.Stopify's abstractions rely on first-class continuations, which it provides by compiling JavaScript to JavaScript. We also identify sub-languages of JavaScript that compilers implicitly use, and exploit these to improve performance. Finally, Stopify needs to repeatedly interrupt and resume program execution. We use a sampling-based technique to estimate program speed that outperforms other systems.Preliminary Solutions There are a handful of robust programming language implementations for the Web: GopherJS (Go) [17], Pyret [57], Skulpt (Python) [68], Doppio (JVM) [77], GambitJS (Scheme) [71], and Whalesong (Racket) [83]. They use sophisticated compilers and runtime systems to support some subset of long-running computations, shared-memory concurrency, blocking I/O, proper tail calls, debugging, and

Teaching Programming to Novices Using the codeBoot Online Environment

“…An alternative to CPS is implemented by Stopify [7], a JavaScript to JavaScript compiler that performs a transformation to allow pausing or interrupting JavaScript code execution before completion. Stopify aims at making JavaScript a better target for high-level languages.…”

Making High-Performance Robots Safe and Easy to Use For an Introduction to Computing

“…Instead, the RoboJS runtime allows students to write simple, straight-line programs (Figure 6b). Its APIs simulate blocking I/O on top of the web browser's non-blocking primitives by building on a tool called Stopify (Baxter et al 2018). Stopify is a source-to-source JavaScript compiler that simulates multiple, cooperative threads of execution in JavaScript.…”