updated no_modules example to show web-sys usage

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(())
 }