无 Bundler

此示例展示了如何使用 `--target web` 标志直接在浏览器中加载代码。对于这种部署策略，不需要像 Webpack 这样的打包器。有关部署的更多信息，请参阅专用文档。

首先，您需要将 `web-sys` 添加到您的 Cargo.toml 中。

[dependencies.web-sys]
version = "0.3.4"
features = [
  'Document',
  'Element',
  'HtmlElement',
  'Node',
  'Window',
]

然后，让我们看一下代码，看看当我们使用 `--target web` 时，我们实际上并没有丢失任何功能！

use wasm_bindgen::prelude::*;

// Called when the wasm module is instantiated
#[wasm_bindgen(start)]
fn main() -> Result<(), JsValue> {
    // Use `web_sys`'s global `window` function to get a handle on the global
    // window object.
    let window = web_sys::window().expect("no global `window` exists");
    let document = window.document().expect("should have a document on window");
    let body = document.body().expect("document should have a body");

    // Manufacture the element we're gonna append
    let val = document.create_element("p")?;
    val.set_inner_html("Hello from Rust!");

    body.append_child(&val)?;

    Ok(())
}

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

否则，其余的部署魔法发生在 `index.html` 中

<html>
  <head>
    <meta content="text/html;charset=utf-8" http-equiv="Content-Type"/>
  </head>
  <body>
    <!-- Note the usage of `type=module` here as this is an ES6 module -->
    <script type="module">
      // Use ES module import syntax to import functionality from the module
      // that we have compiled.
      //
      // Note that the `default` import is an initialization function which
      // will "boot" the module and make it ready to use. Currently browsers
      // don't support natively imported WebAssembly as an ES module, but
      // eventually the manual initialization won't be required!
      import init, { add } from './pkg/without_a_bundler.js';

      async function run() {
        // First up we need to actually load the wasm file, so we use the
        // default export to inform it where the wasm file is located on the
        // server, and then we wait on the returned promise to wait for the
        // wasm to be loaded.
        //
        // It may look like this: `await init('./pkg/without_a_bundler_bg.wasm');`,
        // but there is also a handy default inside `init` function, which uses
        // `import.meta` to locate the wasm file relatively to js file.
        //
        // Note that instead of a string you can also pass in any of the
        // following things:
        //
        // * `WebAssembly.Module`
        //
        // * `ArrayBuffer`
        //
        // * `Response`
        //
        // * `Promise` which returns any of the above, e.g. `fetch("./path/to/wasm")`
        //
        // This gives you complete control over how the module is loaded
        // and compiled.
        //
        // Also note that the promise, when resolved, yields the wasm module's
        // exports which is the same as importing the `*_bg` module in other
        // modes
        await init();

        // And afterwards we can use all the functionality defined in wasm.
        const result = add(1, 2);
        console.log(`1 + 2 = ${result}`);
        if (result !== 3)
          throw new Error("wasm addition doesn't work!");
      }

      run();
    </script>
  </body>
</html>

注意：由于 CORS 限制，您不能直接在 Web 浏览器中打开 `index.html`。相反，您可以使用 Python 的内置 HTTP 服务器设置一个简单的开发环境
wasm-pack build --target web
python3 -m http.server 8080
如果您没有安装 Python，您也可以使用 miniserve，它可以通过 Cargo 安装
cargo install miniserve
miniserve . --index "index.html" -p 8080

就是这样！请务必阅读有关部署选项的内容，以了解无 Bundler 部署的含义。

使用旧的 `--target no-modules`

查看完整源代码

使用 `wasm-bindgen` 无 Bundler 的旧版本是使用 `--target no-modules` 标志传递给 `wasm-bindgen` CLI。

虽然与较新的 `--target web` 类似，但 `--target no-modules` 标志有一些注意事项

它不支持本地 JS 代码片段
它不会生成 ES 模块
它不支持在文档之外使用 `--split-linked-modules`，例如在工作线程中

考虑到这一点，主要区别在于 wasm/JS 代码的加载方式，以下是如何加载与上面相同的模块的 `wasm-pack` 输出的示例。

<html>
  <head>
    <meta content="text/html;charset=utf-8" http-equiv="Content-Type"/>
  </head>
  <body>
    <!-- Include the JS generated by `wasm-pack build` -->
    <script src='pkg/without_a_bundler_no_modules.js'></script>

    <script>
      // Like with the `--target web` output the exports are immediately
      // available but they won't work until we initialize the module. Unlike
      // `--target web`, however, the globals are all stored on a
      // `wasm_bindgen` global. The global itself is the initialization
      // function and then the properties of the global are all the exported
      // functions.
      //
      // Note that the name `wasm_bindgen` can be configured with the
      // `--no-modules-global` CLI flag
      const { add } = wasm_bindgen;

      async function run() {
        await wasm_bindgen();

        const result = add(1, 2);
        console.log(`1 + 2 = ${result}`);
      }

      run();
    </script>
  </body>
</html>

`wasm-bindgen` 指南

无 Bundler

使用旧的 `--target no-modules`