Peter Nemeth

asm.js, the low-level subset of JavaScript, and recently WebAssembly, a completely new portable and efficient compilation target supported by all the major browsers, enables running native applications at near native speed on the Web using the Emscripten compiler.

These technologies are already stable and do amazing work but there is no magic flick which makes your carefully crafted application run the same way it runs on a native platform.

This talk will cover how at Prezi we recently ported our cross-platform viewer application written in C++ to the browser. After a short introduction to Emscripten, asm.js and WebAssembly we will go through our journey leading to production. Main topics will revolve around the restrictions of running in a browser like:

• program loading: options to speed up the JIT / AOT compilation step which has a negative effect on the user experience
• memory handling: duality of memory, especially when interacting with the browser environment
• concurrent execution: with the lack of shared memory how to get the most out of Web Workers and how we implemented a partly compile-time C++ job system API the browser