javascript - Using Promise.reject() in asyncawait catch handler - Stack Overflow

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I just wanted to know if it's a good practice to use the following code:

   const myFun = async () => {
     try {
         const response = await api();
         if(response.status === 200) {
            return response.data;
         }
      } catch(err) {
         return Promise.reject(err);
      }
   }

Here myFun will return a resolved/reject Promise that will be caught by another function. I just wanted to know if this is right way or are there any alternatives?

I just wanted to know if it's a good practice to use the following code:

   const myFun = async () => {
     try {
         const response = await api();
         if(response.status === 200) {
            return response.data;
         }
      } catch(err) {
         return Promise.reject(err);
      }
   }

Here myFun will return a resolved/reject Promise that will be caught by another function. I just wanted to know if this is right way or are there any alternatives?

• javascript
• reactjs
• async-await
• es6-promise

Share Improve this question Follow edited Jun 11, 2020 at 22:51 Fateh AK asked Jun 11, 2020 at 22:13 Fateh AKFateh AK 39666 silver badges2222 bronze badges 2

• 1 For a function marked as async the correct way is to throw – slebetman Commented Jun 11, 2020 at 22:21
• What do you want to happen when the promise resolves, but status code is not 200? You are resolving with undefined when that happens now which is probably not what you want. – jfriend00 Commented Jun 11, 2020 at 23:47

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2 Answers 2

Sorted by: Reset to default 4

You are achieving nothing by trying to re-throw the error from api().

Using async function will cause Promise.reject(error) to be called implicitly when an error is thrown anyway.

Just write your function like this:

const myFun = async () => {
     const response = await api();
     if (response.status === 200) {
          return response.data;
     }
     // You might want to return something else here
}

Then the calling function will still receive the error:

try {
    await myFun();
} catch (error) {
    // error still received
}

What you are doing is mixing async/await and Promises. You can just throw the err from inside the catch block.

const myFun = async () => {
     try {
         const response = await api();
         if(response.status === 200) {
            return response.data;
         }
      } catch(err) {
         throw err;
      }
   }

After this you can catch the error wherever you call myFun.

The end result in both cases would be the same. The only difference is that throw can be used anywhere in JS code but Promise.reject can only be called from within an asynchronous code block only

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