gistfile1.js

function async(f) {
    return function() {
        const generator = f.apply(this, arguments);
        return new Promise(function(resolve, reject) {
            function continue_(value) {
                let result;
                try {
                    result = generator.next(value);
                } catch (e) {
                    reject(e);
                    return;
                }

                if (result.done) {
                    resolve(result.value);
                } else {
                    const promise = result.value;
                    promise.then(function(value) {
                        continue_(value);
                    }, function(e) {
                        generator.throw(e);
                    });
                }
            };

            continue_(undefined);
        });
    };
}