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Hands-On JavaScript High Performance

You're reading from   Hands-On JavaScript High Performance Build faster web apps using Node.js, Svelte.js, and WebAssembly

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Product type Paperback
Published in Feb 2020
Publisher Packt
ISBN-13 9781838821098
Length 376 pages
Edition 1st Edition
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Author (1):
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Justin Scherer Justin Scherer
Author Profile Icon Justin Scherer
Justin Scherer
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Table of Contents (15) Chapters Close

Preface 1. Tools for High Performance on the Web 2. Immutability versus Mutability - The Balance between Safety and Speed FREE CHAPTER 3. Vanilla Land - Looking at the Modern Web 4. Practical Example - A Look at Svelte and Being Vanilla 5. Switching Contexts - No DOM, Different Vanilla 6. Message Passing - Learning about the Different Types 7. Streams - Understanding Streams and Non-Blocking I/O 8. Data Formats - Looking at Different Data Types Other Than JSON 9. Practical Example - Building a Static Server 10. Workers - Learning about Dedicated and Shared Workers 11. Service Workers - Caching and Making Things Faster 12. Building and Deploying a Full Web Application 13. WebAssembly - A Brief Look into Native Code on the Web 14. Other Books You May Enjoy

Writing WebAssembly modules

A WebAssembly module is similar to a JavaScript module. We need to explicitly import anything we need from other WebAssembly/JavaScript modules. Whatever we write in our WebAssembly module can't be found by another WebAssembly module unless we explicitly export it. We can think of it as a JavaScript module – it is a sandboxed environment.

Let's start off with the most basic and useless version of a WebAssembly module:

(module)

With this, we can go to the command line and run the following command:

> wat2wasm useless.wat

This preceding code will spit out a file with the wasm extension. This is what we need to pass into the web browser to run WebAssembly. All this shows us is that WebAssembly, just like ESNext for JavaScript, wants to have everything declared in modules. It is easier to think of it like so, which is what happens when...

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