Promiseからasync-awaitへの変換

Promise

 function restaurantCustomer() {
     return getCustomer()
     .then(customer => {
         return getOrder(customer);
     }).then(order => {
         return prepareFood(order);
     }).then(meal => {
         return serveFood(meal);
     }).then(food => {
         return eatFood(food, customer);
     }).catch(showError);  

async/await

 async function restaurantCustomer() {
     try{
         let customer = await getCustomer();
         let order = await getOrder(customer);
         let meal = await prepareFood(order);
         let food = await serveFood(meal);
         return await eatFood(food);
     } catch(e) {
         showError(e);
     }
 }

参考

https://afteracademy.com/blog/migrating-from-promise-chains-to-async-await