Add closure example

Author: royalicing

readme.md

@@ -24,7 +24,7 @@ import { entry, on, start } from "yieldmachine";
 
 const exampleURL = new URL("https://example.org/");
 function fetchData() {
-  return fetch(exampleURL.toString());
+  return fetch(exampleURL);
 }
 
 function Loader() {
@@ -60,6 +60,56 @@ loader.resolved.then(([response]) => {
 // loader.value; // "success"
 ```
 
+### Passing parameters to a machine with closures
+
+```javascript
+import { entry, on, start } from "yieldmachine";
+
+// Function taking as many arguments as you like
+function GenericLoader(url) {
+  function fetchData() {
+    return fetch(url);
+  }
+  
+  function* idle() {
+    yield on("FETCH", loading);
+  }
+  function* loading() {
+    yield entry(fetchData);
+    yield on("SUCCESS", success);
+    yield on("FAILURE", failure);
+  }
+  function* success() {}
+  function* failure() {
+    yield on("RETRY", loading);
+  }
+
+  return idle;
+}
+
+// Function taking no arguments that will define our machine
+function SpecificLoader() {
+  const exampleURL = new URL("https://example.org/");
+  return GenericLoader(exampleURL);
+}
+
+// Start our specific loader machine
+const loader = start(SpecificLoader);
+loader.value; // "idle"
+
+loader.next("FETCH");
+loader.value; // "loading"
+
+loader.resolved.then(([response]) => {
+  // Use response of fetch()
+  loader.value; // "success"
+});
+
+/* Or with await: */
+// const [response] = await loader.resolved;
+// loader.value; // "success"
+```
+
 ----
 
 Further reading / inspiration: