What causes a runtime exception when a 500 error is thrown, and why isn't it caught by the promise

Question

What causes a runtime exception when a 500 error is thrown, and why isn't it caught by the promise

I encountered an issue with my api call – the server returned a 500 error. I was hoping to handle this error within a Promise, but instead, I received a runtime error TypeError: Failed to fetch, along with a stack trace which prevented me from retrieving the status code. Is there a way for me to access the Response Instance from the api request that includes the status field without encountering a runtime error?

try {
      window.fetch(url, {
            method: 'POST',
            body,
        }).then((res) => { 
                // I am expecting the response here
        }, (rej) => {
                // Or here
        });
    } catch (e) {
      // In cases where the server responds with a 500 error, it gets handled at this level and not inside the promise block
    }

javascript fetch

Answer 1

Answer №1

Since the fetch function works asynchronously, it can exit the try/catch block before resolving or rejecting. To ensure that the code remains inside the try/catch, you must utilize the await keyword like this:

(async () => {
  let data;
  try {
    data = await fetch(url, {
      method: 'GET',
    });
  } catch (error) {
    // Handle errors here
  } finally {
    if(data) {
      // Perform actions with the retrieved data
    }
  }
})()

Answer 2

Since the fetch function works asynchronously, it can exit the try/catch block before resolving or rejecting. To ensure that the code remains inside the try/catch, you must utilize the await keyword like this:

(async () => {
  let data;
  try {
    data = await fetch(url, {
      method: 'GET',
    });
  } catch (error) {
    // Handle errors here
  } finally {
    if(data) {
      // Perform actions with the retrieved data
    }
  }
})()

What causes a runtime exception when a 500 error is thrown, and why isn't it caught by the promise

Answer №1

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