WebAssembly (WASM) for High Performance Apps · レッスン

`wasm-bindgen`による効率的なJS相互運用

`wasm-bindgen`を使いこなし、複雑なデータ構造をシームレスに交換し、Rust WASMとJavaScriptを連携させます

「`wasm-bindgen`による効率的なJS相互運用」はCoddyKit上の無料WebAssembly (WASM) for High Performance Appsレッスンです。これはレッスン3/4です。下記で完全なレッスンを無料で読むことができます。その後、ブラウザ内の組み込みコードエディタと24時間対応のAIチューターでハンズオン演習できます。これはWebAssembly (WASM) for High Performance Apps学習パスの一部であり、ウェブとCoddyKitアプリ全体で進捗が同期されます。 WebAssembly (WASM) for High Performance Appsコースには全4レッスンが含まれています。

このレッスンの一部はまだ翻訳されておらず、英語で表示されています。

Unlocking Complex Interop

Welcome to the final lesson on building high-performance WASM with Rust! So far, you've learned to set up Rust for WASM and write basic functions.

But what about exchanging complex data like strings, objects, or arrays? This is where wasm-bindgen comes in. It's a Rust tool that simplifies interaction between Rust and JavaScript.

What is `wasm-bindgen`?

wasm-bindgen is a utility that helps you create JavaScript bindings for Rust WebAssembly modules. It handles the low-level details of passing data types between the two languages.

Automates FFI: It automatically generates JavaScript glue code and Rust FFI (Foreign Function Interface) declarations.
Rich Type Support: It allows you to pass more complex types like String, JavaScript objects, and even DOM elements directly.
Improved Developer Experience: It makes your Rust WASM modules feel more like native JavaScript modules.

Setting Up for `wasm-bindgen`

To use wasm-bindgen, you need to add it as a dependency in your Cargo.toml. You'll also use the wasm-pack tool, which leverages wasm-bindgen to build your WASM module.

Add this to your Cargo.toml:

[dependencies]
wasm-bindgen = "0.2"

Then, mark your functions with #[wasm_bindgen].

Exporting Basic Functions

Let's start with a simple function. The #[wasm_bindgen] attribute makes a Rust function available to JavaScript.

Try running this example. The add_numbers function is exposed, and run_add_example demonstrates calling it.

use wasm_bindgen::prelude::*;

#[wasm_bindgen]
pub fn add_numbers(a: u32, b: u32) -> u32 {
    a + b
}

// This function serves as a runnable entry point for demonstration.
#[wasm_bindgen]
pub fn run_add_example() -> u32 {
    add_numbers(10, 5)
}

Passing Strings to Rust

One of wasm-bindgen's great features is how it handles strings. You can pass a JavaScript string directly to a Rust function expecting &str or String.

Here, the greet function takes a string argument from JavaScript.

use wasm_bindgen::prelude::*;

#[wasm_bindgen]
pub fn greet(name: &str) -> String {
    format!("Hello, {}!", name)
}

#[wasm_bindgen]
pub fn run_greet_example() -> String {
    greet("CoddyKit User")
}

Returning Strings from Rust

Similarly, Rust functions returning a String will automatically be converted into a JavaScript string. This makes working with text across the boundary very natural.

The get_message function returns a Rust String.

use wasm_bindgen::prelude::*;

#[wasm_bindgen]
pub fn get_message() -> String {
    String::from("This message came from Rust!")
}

#[wasm_bindgen]
pub fn run_get_message_example() -> String {
    get_message()
}

Exporting Structs as JS Classes

wasm-bindgen can also expose Rust structs as JavaScript classes. This allows you to create and manipulate Rust objects directly from JavaScript.

The User struct below becomes a class in JavaScript, complete with a constructor.

use wasm_bindgen::prelude::*;

#[wasm_bindgen]
pub struct User {
    name: String,
    age: u8,
}

#[wasm_bindgen]
impl User {
    #[wasm_bindgen(constructor)]
    pub fn new(name: String, age: u8) -> User {
        User { name, age }
    }
}

#[wasm_bindgen]
pub fn create_user_example() -> User {
    User::new("Alice".to_string(), 30)
}

Adding Methods to JS Classes

Once a Rust struct is exposed as a JavaScript class, you can add methods to its impl block. These methods will be callable directly on the JavaScript object.

Let's add a greet method to our User struct.

use wasm_bindgen::prelude::*;

#[wasm_bindgen]
pub struct User {
    name: String,
    age: u8,
}

#[wasm_bindgen]
impl User {
    #[wasm_bindgen(constructor)]
    pub fn new(name: String, age: u8) -> User {
        User { name, age }
    }

    pub fn greet(&self) -> String {
        format!("Hi, my name is {} and I'm {} years old.", self.name, self.age)
    }
}

#[wasm_bindgen]
pub fn run_user_greet_example() -> String {
    let user = User::new("Bob".to_string(), 25);
    user.greet()
}

Passing Rust Vectors to JS

wasm-bindgen can also handle basic collection types like Vec for primitive types. It will convert a Rust Vec into a JavaScript array.

This allows you to pass lists of numbers or strings easily.

use wasm_bindgen::prelude::*;

#[wasm_bindgen]
pub fn process_numbers(numbers: Vec<u32>) -> Vec<u32> {
    numbers.iter().map(|n| n * 2).collect()
}

#[wasm_bindgen]
pub fn run_process_numbers_example() -> Vec<u32> {
    let input = vec![1, 2, 3];
    process_numbers(input)
}

`wasm-bindgen` Interop Check

Which of the following statements about wasm-bindgen are TRUE?

Recap: Mastering Interop

You've now mastered wasm-bindgen, a powerful tool for seamless interaction between Rust and JavaScript in your WebAssembly projects.

It automates binding generation, making your Rust functions and types easily accessible from JS.
It enables the exchange of complex data types like strings, structs (as JS classes), and vectors.
This significantly improves developer experience, letting you write high-performance Rust logic that feels native in a JavaScript environment.

With wasm-bindgen, your Rust WASM modules can become integral, high-performance components of any web application!

よくある質問

「`wasm-bindgen`による効率的なJS相互運用」レッスンは無料ですか？

はい。「`wasm-bindgen`による効率的なJS相互運用」の完全なテキストはこのウェブで無料で読めます。インタラクティブに演習し（組み込みコードエディタと24時間対応のAIチューター）、WebAssembly (WASM) for High Performance Appsコースの残りをアンロックするには、CoddyKit PROにアップグレードしてください。 WebAssembly (WASM) for High Performance Appsコースには全4レッスンが含まれています。

「`wasm-bindgen`による効率的なJS相互運用」で何を学びますか？

`wasm-bindgen`を使いこなし、複雑なデータ構造をシームレスに交換し、Rust WASMとJavaScriptを連携させますブラウザで直接実行するハンズオンコードでWebAssembly (WASM) for High Performance Appsを演習し、24時間対応のAIチューターがレッスンを進める中での質問に答えます。

WebAssembly (WASM) for High Performance Appsを始めるのに経験は必要ですか？

事前経験は必要ありません。CoddyKitのWebAssembly (WASM) for High Performance Appsは初級者から上級者向けに構成されているため、ここから始めるか最初から始めて、自分のペースで進むことができます。これはレッスン3/4です。

「`wasm-bindgen`による効率的なJS相互運用」レッスンにはどのくらい時間がかかりますか？

ほとんどのCoddyKitレッスンは約5～10分かかります。各レッスンはコンパクトでインタラクティブなので、着実に進歩し、ウェブとアプリ全体で正確に前回の場所から再開できます。

このWebAssembly (WASM) for High Performance Appsレッスンでコードを書いて実行できますか？

はい。すべてのWebAssembly (WASM) for High Performance Appsレッスンに組み込みコードエディタが含まれているため、ブラウザでリアルコードを書いて実行し、即座のAIフィードバックを取得できます。ローカル設定は不要です。

このコースのすべてのレッスン

← WebAssembly (WASM) for High Performance Appsに戻る