Async Await Support in TypeScript and samples

code/async-await/es5/asyncAwaitES5.js

@@ -0,0 +1,70 @@
+var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, generator) {
+    return new (P || (P = Promise))(function (resolve, reject) {
+        function fulfilled(value) { try { step(generator.next(value)); } catch (e) { reject(e); } }
+        function rejected(value) { try { step(generator["throw"](value)); } catch (e) { reject(e); } }
+        function step(result) { result.done ? resolve(result.value) : new P(function (resolve) { resolve(result.value); }).then(fulfilled, rejected); }
+        step((generator = generator.apply(thisArg, _arguments || [])).next());
+    });
+};
+var __generator = (this && this.__generator) || function (thisArg, body) {
+    var _ = { label: 0, sent: function() { if (t[0] & 1) throw t[1]; return t[1]; }, trys: [], ops: [] }, f, y, t, g;
+    return g = { next: verb(0), "throw": verb(1), "return": verb(2) }, typeof Symbol === "function" && (g[Symbol.iterator] = function() { return this; }), g;
+    function verb(n) { return function (v) { return step([n, v]); }; }
+    function step(op) {
+        if (f) throw new TypeError("Generator is already executing.");
+        while (_) try {
+            if (f = 1, y && (t = y[op[0] & 2 ? "return" : op[0] ? "throw" : "next"]) && !(t = t.call(y, op[1])).done) return t;
+            if (y = 0, t) op = [0, t.value];
+            switch (op[0]) {
+                case 0: case 1: t = op; break;
+                case 4: _.label++; return { value: op[1], done: false };
+                case 5: _.label++; y = op[1]; op = [0]; continue;
+                case 7: op = _.ops.pop(); _.trys.pop(); continue;
+                default:
+                    if (!(t = _.trys, t = t.length > 0 && t[t.length - 1]) && (op[0] === 6 || op[0] === 2)) { _ = 0; continue; }
+                    if (op[0] === 3 && (!t || (op[1] > t[0] && op[1] < t[3]))) { _.label = op[1]; break; }
+                    if (op[0] === 6 && _.label < t[1]) { _.label = t[1]; t = op; break; }
+                    if (t && _.label < t[2]) { _.label = t[2]; _.ops.push(op); break; }
+                    if (t[2]) _.ops.pop();
+                    _.trys.pop(); continue;
+            }
+            op = body.call(thisArg, _);
+        } catch (e) { op = [6, e]; y = 0; } finally { f = t = 0; }
+        if (op[0] & 5) throw op[1]; return { value: op[0] ? op[1] : void 0, done: true };
+    }
+};
+function delay(milliseconds, count) {
+    return new Promise(function (resolve) {
+        setTimeout(function () {
+            resolve(count);
+        }, milliseconds);
+    });
+}
+// async function allways return a Promise
+function dramaticWelcome() {
+    return __awaiter(this, void 0, void 0, function () {
+        var i, count;
+        return __generator(this, function (_a) {
+            switch (_a.label) {
+                case 0:
+                    console.log("Hello");
+                    i = 0;
+                    _a.label = 1;
+                case 1:
+                    if (!(i < 5)) return [3 /*break*/, 4];
+                    return [4 /*yield*/, delay(500, i)];
+                case 2:
+                    count = _a.sent();
+                    console.log(count);
+                    _a.label = 3;
+                case 3:
+                    i++;
+                    return [3 /*break*/, 1];
+                case 4:
+                    console.log("World!");
+                    return [2 /*return*/];
+            }
+        });
+    });
+}
+dramaticWelcome();

code/async-await/es5/asyncAwaitES5.ts

@@ -0,0 +1,22 @@
+function delay(milliseconds: number, count: number): Promise<number> {
+    return new Promise<number>(resolve => {
+            setTimeout(() => {
+                resolve(count);
+            }, milliseconds);
+        });
+}
+
+// async function allways return a Promise
+async function dramaticWelcome(): Promise<void> {
+    console.log("Hello");
+
+    for (let i = 0; i < 5; i++) {
+        // await is converting Promise<number> into number
+        const count:number = await delay(500, i);
+        console.log(count);
+    }
+
+    console.log("World!");
+}
+
+dramaticWelcome();

code/async-await/es5/tsconfig.json

@@ -0,0 +1,10 @@
+{
+  "compilerOptions": {
+    "target": "es5",                          /* Specify ECMAScript target version: 'ES3' (default), 'ES5', 'ES2015', 'ES2016', 'ES2017', or 'ESNEXT'. */
+    "module": "commonjs",                     /* Specify module code generation: 'commonjs', 'amd', 'system', 'umd' or 'es2015'. */
+    "lib": ["dom", "es2015.promise", "es5"]  /* Specify library files to be included in the compilation:  */
+  },
+    "files": [
+      "./asyncAwaitES5.ts"
+  ]
+}

code/async-await/es6/asyncAwaitES6.js

@@ -0,0 +1,28 @@
+var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, generator) {
+    return new (P || (P = Promise))(function (resolve, reject) {
+        function fulfilled(value) { try { step(generator.next(value)); } catch (e) { reject(e); } }
+        function rejected(value) { try { step(generator["throw"](value)); } catch (e) { reject(e); } }
+        function step(result) { result.done ? resolve(result.value) : new P(function (resolve) { resolve(result.value); }).then(fulfilled, rejected); }
+        step((generator = generator.apply(thisArg, _arguments || [])).next());
+    });
+};
+function delay(milliseconds, count) {
+    return new Promise(resolve => {
+        setTimeout(() => {
+            resolve(count);
+        }, milliseconds);
+    });
+}
+// async function allways return a Promise
+function dramaticWelcome() {
+    return __awaiter(this, void 0, void 0, function* () {
+        console.log("Hello");
+        for (let i = 0; i < 5; i++) {
+            // await is converting Promise<number> into number
+            const count = yield delay(500, i);
+            console.log(count);
+        }
+        console.log("World!");
+    });
+}
+dramaticWelcome();

code/async-await/es6/asyncAwaitES6.ts

@@ -0,0 +1,22 @@
+function delay(milliseconds: number, count: number): Promise<number> {
+    return new Promise<number>(resolve => {
+            setTimeout(() => {
+                resolve(count);
+            }, milliseconds);
+        });
+}
+
+// async function allways return a Promise
+async function dramaticWelcome(): Promise<void> {
+    console.log("Hello");
+
+    for (let i = 0; i < 5; i++) {
+        // await is converting Promise<number> into number
+        const count:number = await delay(500, i);
+        console.log(count);
+    }
+
+    console.log("World!");
+}
+
+dramaticWelcome();

code/async-await/es6/tsconfig.json

@@ -0,0 +1,9 @@
+{
+  "compilerOptions": {
+    "target": "es6",                          /* Specify ECMAScript target version: 'ES3' (default), 'ES5', 'ES2015', 'ES2016', 'ES2017', or 'ESNEXT'. */
+    "module": "commonjs"                     /* Specify module code generation: 'commonjs', 'amd', 'system', 'umd' or 'es2015'. */
+  },
+    "files": [
+      "./asyncAwaitES6.ts"
+  ]
+}

docs/async-await.md

@@ -45,4 +45,153 @@ const foo = wrapToReturnPromise(function* () {
 
 where the `wrapToReturnPromise` just executes the generator function to get the `generator` and then use `generator.next()`, if the value is a `promise` it would `then`+`catch` the promise and depending upon the result call `generator.next(result)` or `generator.throw(error)`. That's it!
 
+
+
+### Async Await Support in TypeScript
+**Async - Await** has been supported by [TypeScript since version 1.7](https://www.typescriptlang.org/docs/handbook/release-notes/typescript-1-7.html). Asynchronous functions are prefixed with the *async* keyword; *await* suspends the execution until an asynchronous function return promise is fulfilled and unwraps the value from the *Promise* returned.
+It was only supported for **target es6** transpiling directly to **ES6 generators**.
+
+**TypeScript 2.1** [added the capability to ES3 and ES5 run-times](https://www.typescriptlang.org/docs/handbook/release-notes/typescript-2-1.html), meaning you’ll be free to take advantage of it no matter what environment you’re using. It's important to notice that we can use async / await with TypeScript 2.1 and many browsers are supported, of course, having globally added a **polyfill for Promise**.
+
+Let's see this **example** and take a look to this code to figure out TypeScript async / await **notation** works: 
+```ts
+function delay(milliseconds: number, count: number): Promise<number> {
+    return new Promise<number>(resolve => {
+            setTimeout(() => {
+                resolve(count);
+            }, milliseconds);
+        });
+}
+
+// async function allways return a Promise
+async function dramaticWelcome(): Promise<void> {
+    console.log("Hello");
+
+    for (let i = 0; i < 5; i++) {
+        // await is converting Promise<number> into number
+        const count:number = await delay(500, i);
+        console.log(count);
+    }
+
+    console.log("World!");
+}
+
+dramaticWelcome();
+```
+
+**Transpiling to ES6 (--target es6)**
+```js
+var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, generator) {
+    return new (P || (P = Promise))(function (resolve, reject) {
+        function fulfilled(value) { try { step(generator.next(value)); } catch (e) { reject(e); } }
+        function rejected(value) { try { step(generator["throw"](value)); } catch (e) { reject(e); } }
+        function step(result) { result.done ? resolve(result.value) : new P(function (resolve) { resolve(result.value); }).then(fulfilled, rejected); }
+        step((generator = generator.apply(thisArg, _arguments || [])).next());
+    });
+};
+function delay(milliseconds, count) {
+    return new Promise(resolve => {
+        setTimeout(() => {
+            resolve(count);
+        }, milliseconds);
+    });
+}
+// async function allways return a Promise
+function dramaticWelcome() {
+    return __awaiter(this, void 0, void 0, function* () {
+        console.log("Hello");
+        for (let i = 0; i < 5; i++) {
+            // await is converting Promise<number> into number
+            const count = yield delay(500, i);
+            console.log(count);
+        }
+        console.log("World!");
+    });
+}
+dramaticWelcome();
+```
+You can see full example [here][asyncawaites6code].
+
+
+**Transpiling to ES5 (--target es5)**
+```js
+var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, generator) {
+    return new (P || (P = Promise))(function (resolve, reject) {
+        function fulfilled(value) { try { step(generator.next(value)); } catch (e) { reject(e); } }
+        function rejected(value) { try { step(generator["throw"](value)); } catch (e) { reject(e); } }
+        function step(result) { result.done ? resolve(result.value) : new P(function (resolve) { resolve(result.value); }).then(fulfilled, rejected); }
+        step((generator = generator.apply(thisArg, _arguments || [])).next());
+    });
+};
+var __generator = (this && this.__generator) || function (thisArg, body) {
+    var _ = { label: 0, sent: function() { if (t[0] & 1) throw t[1]; return t[1]; }, trys: [], ops: [] }, f, y, t, g;
+    return g = { next: verb(0), "throw": verb(1), "return": verb(2) }, typeof Symbol === "function" && (g[Symbol.iterator] = function() { return this; }), g;
+    function verb(n) { return function (v) { return step([n, v]); }; }
+    function step(op) {
+        if (f) throw new TypeError("Generator is already executing.");
+        while (_) try {
+            if (f = 1, y && (t = y[op[0] & 2 ? "return" : op[0] ? "throw" : "next"]) && !(t = t.call(y, op[1])).done) return t;
+            if (y = 0, t) op = [0, t.value];
+            switch (op[0]) {
+                case 0: case 1: t = op; break;
+                case 4: _.label++; return { value: op[1], done: false };
+                case 5: _.label++; y = op[1]; op = [0]; continue;
+                case 7: op = _.ops.pop(); _.trys.pop(); continue;
+                default:
+                    if (!(t = _.trys, t = t.length > 0 && t[t.length - 1]) && (op[0] === 6 || op[0] === 2)) { _ = 0; continue; }
+                    if (op[0] === 3 && (!t || (op[1] > t[0] && op[1] < t[3]))) { _.label = op[1]; break; }
+                    if (op[0] === 6 && _.label < t[1]) { _.label = t[1]; t = op; break; }
+                    if (t && _.label < t[2]) { _.label = t[2]; _.ops.push(op); break; }
+                    if (t[2]) _.ops.pop();
+                    _.trys.pop(); continue;
+            }
+            op = body.call(thisArg, _);
+        } catch (e) { op = [6, e]; y = 0; } finally { f = t = 0; }
+        if (op[0] & 5) throw op[1]; return { value: op[0] ? op[1] : void 0, done: true };
+    }
+};
+function delay(milliseconds, count) {
+    return new Promise(function (resolve) {
+        setTimeout(function () {
+            resolve(count);
+        }, milliseconds);
+    });
+}
+// async function allways return a Promise
+function dramaticWelcome() {
+    return __awaiter(this, void 0, void 0, function () {
+        var i, count;
+        return __generator(this, function (_a) {
+            switch (_a.label) {
+                case 0:
+                    console.log("Hello");
+                    i = 0;
+                    _a.label = 1;
+                case 1:
+                    if (!(i < 5)) return [3 /*break*/, 4];
+                    return [4 /*yield*/, delay(500, i)];
+                case 2:
+                    count = _a.sent();
+                    console.log(count);
+                    _a.label = 3;
+                case 3:
+                    i++;
+                    return [3 /*break*/, 1];
+                case 4:
+                    console.log("World!");
+                    return [2 /*return*/];
+            }
+        });
+    });
+}
+dramaticWelcome();
+```
+You can see full example [here][asyncawaites5code].
+
+
+**Note**: for both target scenarios, we need to make sure our run-time has an ECMAScript-compliant Promise available globally. That might involve grabbing a polyfill for Promise. We also need to make sure that TypeScript knows Promise exists by setting your lib flag to something like "dom", "es2015" or "dom", "es2015.promise", "es5". 
+**We can see what browsers DO have Promise support (native and polyfilled) [here](https://kangax.github.io/compat-table/es6/#test-Promise).**
+
 [generators]:./generators.md
+[asyncawaites5code]:../code/async-await/es5/asyncAwaitES5.js
+[asyncawaites6code]:../code/async-await/es6/asyncAwaitES6.js