What should I do if 'Uncaught (in promise) Error: Request failed with status code 500' occurs when using axios in a Vue application?

It is very common to use axios in Vue applications. axios is a Promise-based HTTP client that can be used in browsers and Node.js. During the development process, the error message "Uncaught (in promise) Error: Request failed with status code 500" sometimes appears. For developers, this error message may be difficult to understand and solve. This article will explore this problem and its solution.

1. Problem Example

When sending a request to the backend API, sometimes a response is received with "Uncaught (in promise) Error: Request failed with status code 500" " error message. This problem usually occurs when there is a server-side failure or an API error. The following is a code example:

axios.get('/api')
  .then(response => {
    console.log(response)
  })
  .catch(error => {
    console.log(error)
  })

In this example, we send a GET request to the server. If an error occurs, the catch function will be triggered and the error message will be printed. In this case, we may see the following error message:

Uncaught (in promise) Error: Request failed with status code 500
    at createError (createError.js:16)
    at settle (settle.js:18)
    at XMLHttpRequest.handleLoad (xhr.js:77)

2. Cause analysis

The reason for this error message is that the backend API returns HTTP status code 500, that is, "Server Internal Error". When this happens, axios provides error information in the return value's data and includes the response's status code in the error object. Therefore, in our above code, when axios requests the backend API to return a 500 error, it will enter the catch function and output the error message.

There are many reasons why this problem may occur. First, the server may have a software bug or hardware failure that causes an internal error in the request. Secondly, there may be problems with the API code, and some problems will cause the response to return a 500 error.

3. Solution

How to solve this problem? We can use the following methods.

3.1 Check the backend API error information

First, we should check the detailed error information returned by the backend API to better diagnose the problem. You can view request and response information under your browser's Network tab, or you can view the backend server's logs. If an error occurs, there will be a more detailed error message to help us troubleshoot the problem.

3.2 Check the API code

Secondly, we should check the API code and determine whether there is a problem with it. When checking the API code, you should check the following aspects:

• If there are any syntax errors or logical errors.
• Whether the request can be processed correctly and the correct response returned.
• In the development environment, are there any unhandled exceptions?

3.3 Adding error handlers

In Vue applications, we can add error handlers to better manage errors. Here is an example of handling Axios request errors:

axios.get('/api')
  .then(response => {
    console.log(response)
  })
  .catch(error => {
    if (error.response) {
      console.log(error.response.data)
      console.log(error.response.status)
      console.log(error.response.headers)
    } else if (error.request) {
      console.log(error.request)
    } else {
      console.log('Error', error.message)
    }
    console.log(error.config)
  })

In this example, we have used if statements to check different parts of the error object. If the error object contains a response object, we can access the response data. If there is no response object in the error object, we will output the error message.

4. Summary

When using HTTP requests in Vue applications and axios, the error message "Uncaught (in promise) Error: Request failed with status code 500" appears. Usually caused by server configuration issues or API errors. To solve this problem, we need to check the error information returned by the API and handle it correctly. Once you do this, you can better understand the cause of the error and take better steps to avoid the problem.

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