Book Image

Learn WebAssembly

By : Mike Rourke
Book Image

Learn WebAssembly

By: Mike Rourke

Overview of this book

WebAssembly is a brand-new technology that represents a paradigm shift in web development. This book teaches programmers to leverage this technology to write high-performance applications that run in the browser. This book introduces you to powerful WebAssembly concepts to help you write lean and powerful web applications with native performance. You start with the evolution of web programming, the state of things today, and what can be done with the advent and release of WebAssembly. We take a look at the journey from JavaScript to asm.js to WebAssembly. We then move on to analyze the anatomy of a WebAssembly module and the relationship between binary and text formats, along with the corresponding JavaScript API. Further on, you'll implement all the techniques you've learned to build a high-performance application using C and WebAssembly, and then port an existing game written in C++ to WebAssembly using Emscripten. By the end of this book, you will be well-equipped to create high-performance applications and games for the web using WebAssembly.
Table of Contents (18 chapters)
Title Page
Copyright and Credits
Dedication
PacktPub.com
Contributors
Preface
Index

Loading the Emscripten module


Loading and interacting with a module that utilizes Emscripten's glue code is considerably different from WebAssembly's JavaScript API. This is because Emscripten provides additional functionality for interacting with the JavaScript code. In this section, we're going to discuss the loading code that Emscripten provides when outputting an HTML file and review the process for loading an Emscripten module in the browser.

Pre-generated loading code

If you specify -o <target>.html when running the emcc command, Emscripten generates an HTML file and automatically adds code to load the module to the end of the file. Here's what the loading code in the HTML file looks like with the contents of each Module function excluded:

var statusElement = document.getElementById('status');
var progressElement = document.getElementById('progress');
var spinnerElement = document.getElementById('spinner');

var Module = {
  preRun: [],
  postRun: [],
  print: (function() {...}...