在 for 循环中使用 async/await 不等待异步方法调用

Question

My async method getNumFruit is not getting called for my below code

const fruitsToGet = ['apple', 'grape', 'pear']
const fruitBasket = {
  apple: 27, 
  grape: 0,
  pear: 14 
}
console.log("start");




async function getNumFruit(fruit) {
   console.log("iside")
  return sleep(1000).then(v => fruitBasket[fruit])
}

async function test(){
    console.log("inside test");

  for(i=0;i++;i<fruitsToGet.length){
  console.log("start2");

    const fruit = fruitsToGet[index]
    const numFruit = await getNumFruit(fruit)
    console.log(numFruit)

  }
  return "done";
}
var result = test();
console.log(result)

console.log("end!!!!!")

can someone help me understanding what I am doing wrong here!

Answer 1

There are lots of things wrong here:

1. Your for loop needs to be for (let i = 0; i < fruitsToGet.length; i++) { so you both declare the loop variable and increment it in the right place.
2. Then, you need to use i , not index in your loop.
3. Then, you need to use test().then(result => console.log(result)) to know when test() is actually done because it's an async function so it returns a promise that you have to monitor with .then() or await to know when it's done.
4. You don't show the code for the function sleep() .

Take a look at this fixed up code which you can run in this snippet to see the results for yourself:

 const fruitsToGet = ['apple', 'grape', 'pear']; const fruitBasket = { apple: 27, grape: 0, pear: 14 }; console.log("start"); function sleep(t) { return new Promise(resolve => { setTimeout(resolve, t); }); } function getNumFruit(fruit) { console.log("iside") return sleep(1000).then(v => fruitBasket[fruit]); } async function test(){ console.log("inside test"); for (let i = 0; i < fruitsToGet.length; i++) { console.log("start loop invocation", i); const fruit = fruitsToGet[i]; const numFruit = await getNumFruit(fruit); console.log(numFruit); } return "done"; } test().then(result => { console.log(result); console.log("end!!!!!") });

When you run it, it generates this output:

start
inside test
start loop invocation 0
iside
27
start loop invocation 1
iside
0
start loop invocation 2
iside
14
done
end!!!!!