如何访问Fetch返回值中的变量？

Question

我有一个产品页面，上面有一个按钮(addToCart)，然后我使用fetch将产品添加到 req.session.cart 在服务器上。在应用程序的前台，我使用fetch与服务器进行通信，并获得了服务器上的 req.session.cart 作为一个返回值。如何将获取的结果分配给外部变量？

let whatevervariablehere    

function addToCart(e){



  let items = e.target.parentElement.parentElement
   // rest of the clicked item code .....


  //fetch and send the data to server so you can update session
  fetch('sc8', {
  method: 'POST',
  headers: {
  'Accept': 'application/json',
  'Content-type': 'application/json',
  },
  body: JSON.stringify({
  title : title,
  price : price,
  description : description,
  id : id
  })
  }).then(response => response.json()).then((results) => {

//**this is the part I'm talking about**
console.log("|||||results|||||", results)
//**How to get access to "retrievelocalstorage" from outside of this code**
      localstorage = window.localStorage.setItem(JSON.stringify(user), JSON.stringify(results));
      retrievelocalstorage = JSON.parse(window.localStorage.getItem(JSON.stringify(user))) || "No items in cart, Yet!";
       // the below console.log prints the right results
      console.log("retrievelocalstorage", retrievelocalstorage)

      })  //results function end
      .catch(error => console.log(error));



      } //end of addTocart Function



// this prints "outside the addToCart" and nothing else.
// it is outside the addToCart fn and the fetch promise.
// can I have access to retrievelocalstorage value out here, out of the 
//   function and the promise or not?
  **console.log("this is outside the addToCart fn", retrievelocalstorage)**

是否可以获得对 retrievelocalstorage 外边的结果fn？

编辑1console.log("this is outside the addToCart fn", retrievelocalstorage)并没有打印retrievelocalstorage的值，所以建议添加.then(retrievelocalstorage => whatevervariablehere = retrievelocalstorage)在consolelog中仍然显示whatevervariable为空。

Answer 1

你可以尝试在这里使用asyncawait，这样你就不会使用了。.then 并可以将结果分配给一个变量。

async function getResults() {
  const result = await fetch(...).json() // your code for fetch
  // work with result as a regular variable
}

Answer 2

你是在async上下文中。你应该继续在承诺里面工作。

.then(() => {
   // you can get your data from LocalStorage here
})

后面的代码 fetch 不劳而获

或者你可以将异步 fn 封装到另一个 fn 中，然后使用 async/await

async function() {
  await addToCart...
  // you can get your data from LocalStorage here
}