Clean up & annotate code. Fixes #8.

Author: developit

greenlet.js

@@ -1,25 +1,51 @@
 /** Move an async function into its own thread.
- *  @param {Function} fn	The (async) function to run in a Worker.
+ *  @param {Function} asyncFunction  An (async) function to run in a Worker.
  */
-export default function greenlet(fn) {
-	let w = new Worker(URL.createObjectURL(new Blob([
-			'onmessage=('+(
-				f => ({ data }) => Promise.resolve().then(
-					() => f.apply(f, data[1])
-				).then(
-					d => { postMessage([data[0], null, d]); },
-					e => { postMessage([data[0], ''+e]); }
-				)
-			)+')('+fn+')'
-		]))),
-		c = 0,
-		p = {};
-	w.onmessage = ({ data: [c,e,d] }) => {
-		p[c][e?1:0](e||d);
-		delete p[c];
+export default function greenlet(asyncFunction) {
+	// Create an "inline" worker
+	let worker = new Worker(
+			// The URL is a pointer to a stringified function (as a blob object)
+			URL.createObjectURL(
+				new Blob([
+					// Register our wrapper function as the message handler
+					'onmessage=('+(
+						// f() is the user-supplied async function
+						userFunc => ({ data }) => Promise.resolve().then(
+							// invoking within then() captures exceptions in f() as rejections
+							() => userFunc.apply(userFunc, data[1])
+						).then(
+							d => {
+								// success handler - callback(id, null, result)
+								postMessage([data[0], null, d]);
+							},
+							e => {
+								// error handler - callback(id, err)
+								postMessage([data[0], ''+e]);
+							}
+						)
+					)+')('+asyncFunction+')'  // pass user-supplied function to the closure
+				])
+			)
+		),
+
+		// A simple counter is used to generate worker-global unique ID's for RPC:
+		currentId = 0,
+
+		// Outward-facing promises store their "controllers" (`[request, reject]`) here:
+		promises = {};
+
+	// Handle RPC results/errors coming back out of the worker
+	worker.onmessage = ({ data: [id, err, result] }) => {
+		// invoke the promise's resolve() or reject() depending on whether there was an error.
+		promises[id][err ? 1 : 0](err || result);
+		// ... then delete the promise controller
+		delete promises[id];
 	};
-	return (...a) => new Promise( (y, n) => {
-		p[++c] = [y, n];
-		w.postMessage([c, a]);
+
+	// Return a proxy function that forwards calls to the worker & returns a promise for the result.
+	return (...args) => new Promise( (resolve, reject) => {
+		promises[++currentId] = [resolve, reject];
+		// Send an RPC call to the worker - call(id, params)
+		worker.postMessage([currentId, args]);
 	});
 }

package.json

@@ -11,7 +11,10 @@
     "release": "npm run -s prepare && npm test && git commit -am $npm_package_version && git tag $npm_package_version && git push && git push --tags && npm publish"
   },
   "eslintConfig": {
-    "extends": "eslint-config-developit"
+    "extends": "eslint-config-developit",
+    "rules": {
+      "prefer-spread": 0
+    }
   },
   "files": [
     "greenlet.js",