async-await.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 (sent[0] === 1) throw sent[1]; return sent[1]; }, trys: [], stack: [] }, sent, f;
    function step(op) {
        if (f) throw new TypeError("Generator is already executing.");
        while (1) {
            if (_.done) switch (op[0]) {
                case 0: return { value: void 0, done: true };
                case 1: case 6: throw op[1];
                case 2: return { value: op[1], done: true };
            }
            try {
                switch (f = 1, op[0]) {
                    case 0: case 1: sent = op; break;
                    case 4: return _.label++, { value: op[1], done: false };
                    case 7: op = _.stack.pop(), _.trys.pop(); continue;
                    default:
                        var r = _.trys.length > 0 && _.trys[_.trys.length - 1];
                        if (!r && (op[0] === 6 || op[0] === 2)) { _.done = 1; continue; }
                        if (op[0] === 3 && (!r || (op[1] > r[0] && op[1] < r[3]))) { _.label = op[1]; break; }
                        if (op[0] === 6 && _.label < r[1]) { _.label = r[1], sent = op; break; }
                        if (r && _.label < r[2]) { _.label = r[2], _.stack.push(op); break; }
                        if (r[2]) { _.stack.pop(); }
                        _.trys.pop();
                        continue;
                }
                op = body.call(thisArg, _);
            }
            catch (e) { op = [6, e]; }
            finally { f = 0, sent = void 0; }
        }
    }
    return {
        next: function (v) { return step([0, v]); },
        "throw": function (v) { return step([1, v]); },
        "return": function (v) { return step([2, v]); }
    };
};
function y(num) {
    return __awaiter(this, void 0, void 0, function () {
        return __generator(this, function (_a) {
            return [2 /*return*/, 3 + num];
        });
    });
}
function x() {
    return __awaiter(this, void 0, void 0, function () {
        var e, x_1;
        return __generator(this, function (_a) {
            switch (_a.label) {
                case 0:
                    _a.trys.push([0, 2, , 3]);
                    return [4 /*yield*/, y(3)];
                case 1:
                    e = _a.sent();
                    return [2 /*return*/, e + 1];
                case 2:
                    x_1 = _a.sent();
                    return [2 /*return*/, x_1];
                case 3: return [2 /*return*/];
            }
        });
    });
}

async-await.ts

interface Thenable<R> {
    then<U>(onFulfilled?: (value: R) => U | Thenable<U>,  onRejected?: (error: any) => U | Thenable<U>): Thenable<U>;
}

declare class Promise<R> implements Thenable<R> {
    then<U>(onFulfilled?: (value: R) => U | Thenable<U>,  onRejected?: (error: any) => U | Thenable<U>): Promise<U>;
}

async function y(num: number): Promise<number> {
  return 3 + num;
}

async function x(): Promise<number> {
  try {
    var e = await y(3);
    return e + 1;
  } catch (x) {
    return x;
  }
}

package.json

{
  "name": "temp",
  "version": "1.0.0",
  "dependencies": {
    "typescript": "^2.1.0-dev.20160907"
  }
}

tsconfig.json

{
    "compilerOptions": {
        "module": "commonjs",
        "target": "es5",
        "noImplicitAny": false,
        "sourceMap": false
    }
}