updated no_modules example to show web-sys usage

examples/no_modules/Cargo.toml

@@ -8,3 +8,13 @@ crate-type = ["cdylib"]
 
 [dependencies]
 wasm-bindgen = "0.2.28"
+
+[dependencies.web-sys]
+version = "0.3.4"
+features = [
+  'Document',
+  'Element',
+  'HtmlElement',
+  'Node',
+  'Window',
+]

examples/no_modules/index.html

@@ -20,19 +20,15 @@
     <script src='./no_modules.js'></script>
 
     <script>
-      // the `wasm_bindgen` global is set to the exports of the Rust module
-      const { greet } = wasm_bindgen;
-
-      // we'll defer our execution until the wasm is ready to go
-      function run() {
-          greet('World');
-      }
-
-      // here we tell bindgen the path to the wasm file so it can run
-      // initialization and return to us a promise when it's done
-      wasm_bindgen('./no_modules_bg.wasm')
-        .then(run)
-        .catch(console.error);
+      window.addEventListener('load', async () => {
+          // the `wasm_bindgen` global is set to the exports of the Rust module
+          //
+          // here we tell bindgen the path to the wasm file so it can run
+          // initialization and return to us a promise when it's done
+          // also, we can use 'await' on the returned promise
+          await wasm_bindgen('./no_modules_bg.wasm');
+          wasm_bindgen.run();
+      });
     </script>
   </body>
 </html>

examples/no_modules/src/lib.rs

@@ -1,13 +1,22 @@
 extern crate wasm_bindgen;
+extern crate web_sys;
 
 use wasm_bindgen::prelude::*;
 
+// Called by our JS entry point to run the example
 #[wasm_bindgen]
-extern "C" {
-    fn alert(s: &str);
-}
+pub fn run() -> 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");
 
-#[wasm_bindgen]
-pub fn greet(name: &str) {
-    alert(&format!("Hello, {}!", name));
+    // 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(())
 }