initial port of the UI kit

go/cmd/examples/go-wasm-web/wwwroot/wasmboot.js

@@ -0,0 +1,24 @@
+// bootstrap.js — boots the Go/Wasm client, and supports flash-free hot swaps.
+//
+// On first load the server has already rendered the page's HTML into #app and
+// the wasm app hydrates it (see wasm/main.go). The dev server's livereload
+// script hot-swaps a freshly built module WITHOUT a full page reload or a blank
+// flash: it calls __gowasmPrepare() to fetch + compile the new module while the
+// current page is still visible, then (in one synchronous step) __gowasmDispose()
+// to tear down the old instance and start() to run the new one.
+(function () {
+  // prepare fetches + compiles the module and returns a SYNCHRONOUS start()
+  // thunk. Separating the async work (network + compile) from start (which
+  // renders synchronously) is what lets a swap avoid an intermediate blank #app.
+  async function prepare() {
+    const go = new Go();
+    // cache:no-store so a hot swap always fetches the freshly built bytes.
+    const resp = await fetch("/app.wasm", { cache: "no-store" });
+    const result = await WebAssembly.instantiateStreaming(resp, go.importObject);
+    return function start() { go.run(result.instance); }; // runs main() (renders), then parks on select{}
+  }
+  async function boot() { (await prepare())(); }
+  window.__gowasmPrepare = prepare;
+  window.__gowasmBoot = boot;
+  boot();
+})();