Add an example of DOM access

examples/dom/src/lib.rs

@@ -0,0 +1,39 @@
+#![feature(proc_macro)]
+
+extern crate wasm_bindgen;
+
+use wasm_bindgen::prelude::*;
+
+// Definitions of the functionality available in JS, which wasm-bindgen will
+// generate shims for today (and eventually these should be near-0 cost!)
+//
+// These definitions need to be hand-written today but the current vision is
+// that we'll use WebIDL to generate this `extern` block into a crate which you
+// can link and import. There's a tracking issue for this at
+// https://github.com/alexcrichton/wasm-bindgen/issues/42
+//
+// In the meantime these are written out by hand and correspond to the names and
+// signatures documented on MDN, for example
+#[wasm_bindgen]
+extern {
+    type HTMLDocument;
+    static document: HTMLDocument;
+    #[wasm_bindgen(method)]
+    fn createElement(this: &HTMLDocument, tagName: &str) -> Element;
+    #[wasm_bindgen(method, getter)]
+    fn body(this: &HTMLDocument) -> Element;
+
+    type Element;
+    #[wasm_bindgen(method, setter)]
+    fn set_innerHTML(this: &Element, html: &str);
+    #[wasm_bindgen(method)]
+    fn appendChild(this: &Element, other: Element);
+}
+
+// Called by our JS entry point to run the example
+#[wasm_bindgen]
+pub fn run() {
+    let val = document.createElement("p");
+    val.set_innerHTML("Hello from Rust!");
+    document.body().appendChild(val);
+}