Nuxt•2w ago

Kinda lost on how to handle errors on thrown on server properly on the client

i'm doing some validation on payload of the a login api i've got using, and i check the instance of the error being thrown to get something to work with on the frontend, but its the 500 error that's being thrown instead, i'm loosing my mind

8 Replies

kapa.ai•2w ago

Hi @Tobi. I'm kapa.ai, your friendly support bot. I will try to answer your question by searching through the knowledge base. :wave: ---------------------- When handling errors thrown on the server in Nuxt (for example, from an API route), it's important to use Nuxt's built-in error utilities to ensure that meaningful error information is passed to the client. How to Throw Custom Errors in API Routes Instead of just throwing a generic Error, use Nuxt's createError utility in your server API routes. This allows you to set a custom statusCode, statusMessage, and even a data property for extra details:

export default defineEventHandler((event) => {
  const body = await readBody(event)
  if (!body.username) {
    throw createError({
      statusCode: 400,
      statusMessage: 'Username is required',
      data: { field: 'username' }
    })
  }
  // ...rest of your logic
})

export default defineEventHandler((event) => {
  const body = await readBody(event)
  if (!body.username) {
    throw createError({
      statusCode: 400,
      statusMessage: 'Username is required',
      data: { field: 'username' }
    })
  }
  // ...rest of your logic
})

See docs example How to Access the Error on the Client When you use composables like useFetch or $fetch on the client, you can catch the error and access the properties you set (statusCode, statusMessage, and data). For example:

try {
  await $fetch('/api/login', { method: 'POST', body: { ... } })
} catch (error) {
  // error.statusCode, error.statusMessage, error.data are available
  console.log(error.statusCode)      // 400
  console.log(error.statusMessage)   // 'Username is required'
  console.log(error.data)            // { field: 'username' }
}

try {
  await $fetch('/api/login', { method: 'POST', body: { ... } })
} catch (error) {
  // error.statusCode, error.statusMessage, error.data are available
  console.log(error.statusCode)      // 400
  console.log(error.statusMessage)   // 'Username is required'
  console.log(error.data)            // { field: 'username' }
}

See createError API docs Important: If you throw a plain Error or don't use createError, Nuxt will default to a 500 Internal Server Error, and you won't get your custom message or data on the client. Always use createError for custom error handling in API routes. Passing Custom Data If you want to pass additional data to the client, use the data property in createError. This is the recommended way to send structured error information to the frontend, as the message property may not always propagate from server to client in API routes, but statusMessage and data will.

In API routes, using createError by passing an object with a short statusMessage is recommended because it can be accessed on the client side. Otherwise, a message passed to createError on an API route will not propagate to the client. Alternatively, you can use the data property to pass data back to the client.

createError API docs --- Summary:
- Use createError in your server API routes for custom errors. - Access statusCode, statusMessage, and data on the client in your error handler. - Avoid throwing plain Error objects if you want custom error info on the client. If you follow this pattern, you should be able to handle and display server-thrown errors on the client as intended. ---------------------- Note: you can ask me a follow up question by @ mentioning me again :speech_balloon: ----------------------

kapa.ai•2w ago

<@642130694394478612> Kapa.ai is still learning and improving, please let me know how I did by reacting below.

TobiOP•2w ago

@kapa.ai are try-catch not a thing in nuxt's server api defineEventHandler thingamabob?

kapa.ai•2w ago

Let me check the knowledge base for you again. One moment! :books: ---------------------- Yes, you can absolutely use try-catch blocks inside Nuxt server API routes defined with defineEventHandler. This is a standard way to handle errors that may occur during the execution of your handler logic. For example, you might see code like this:

export default defineEventHandler(async (event) => {
  try {
    // Your logic here, e.g. reading the body, querying a database, etc.
    const body = await readBody(event)
    // ... more logic
    return { success: true }
  } catch (error) {
    // Handle or re-throw the error
    throw createError({
      statusCode: 400,
      statusMessage: 'Custom error message',
      data: { details: error.message }
    })
  }
})

export default defineEventHandler(async (event) => {
  try {
    // Your logic here, e.g. reading the body, querying a database, etc.
    const body = await readBody(event)
    // ... more logic
    return { success: true }
  } catch (error) {
    // Handle or re-throw the error
    throw createError({
      statusCode: 400,
      statusMessage: 'Custom error message',
      data: { details: error.message }
    })
  }
})

This pattern is shown in community examples as well, where errors are caught and either logged or re-thrown as a custom error using createError, which is the recommended way to send structured error information to the client in Nuxt API routes see example. So, try-catch is definitely a thing in Nuxt server API handlers! ---------------------- Note: you can ask me a follow up question by @ mentioning me again :speech_balloon: ----------------------

kapa.ai•2w ago

<@642130694394478612> Kapa.ai is still learning and improving, please let me know how I did by reacting below.

TobiOP•2w ago

@kapa.ai , alright i readValidatedBody using a zod schema and my error generates from there and checking the error instance in the catch block doesnt seem to be working

kapa.ai•2w ago

Let me check the knowledge base for you again. One moment! :books: ---------------------- When you use readValidatedBody with a Zod schema in a Nuxt server API route, if the validation fails, an error is thrown. However, the type and structure of this error may not be a standard JavaScript Error or a Zod error directly—it is handled internally by Nuxt/Nitro. The knowledge sources do not provide explicit details about the exact error instance or type thrown by readValidatedBody. However, the Nuxt documentation shows that you can use a try-catch block around your handler logic, and you can throw a custom error using createError in the catch block if you want to control the error response. Here’s a pattern you can use:

export default defineEventHandler(async (event) => {
  try {
    const body = await readValidatedBody(event, yourZodSchema.parse)
    // ... your logic
    return { success: true }
  } catch (error) {
    // You can inspect the error here, but its structure may depend on Nitro's implementation.
    // To ensure a consistent response, wrap it in createError:
    throw createError({
      statusCode: 400,
      statusMessage: 'Validation failed',
      data: error // You can pass the error details here for debugging or client display
    })
  }
})

export default defineEventHandler(async (event) => {
  try {
    const body = await readValidatedBody(event, yourZodSchema.parse)
    // ... your logic
    return { success: true }
  } catch (error) {
    // You can inspect the error here, but its structure may depend on Nitro's implementation.
    // To ensure a consistent response, wrap it in createError:
    throw createError({
      statusCode: 400,
      statusMessage: 'Validation failed',
      data: error // You can pass the error details here for debugging or client display
    })
  }
})

See Nuxt server error handling Key points: - The error thrown by readValidatedBody may not be a Zod error instance directly, so instanceof checks may not work as expected. - For consistent client-side error handling, always wrap and re-throw with createError in your catch block, passing relevant details in the data property. If you need to access specific validation error details on the client, include them in the data property of your custom error. If you need more granular control or want to check for Zod errors specifically, you may need to validate manually with Zod and handle the result, but this is not shown in the official Nuxt documentation. ---------------------- Note: you can ask me a follow up question by @ mentioning me again :speech_balloon: ----------------------

kapa.ai•2w ago

<@642130694394478612> Kapa.ai is still learning and improving, please let me know how I did by reacting below.

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Kinda lost on how to handle errors on thrown on server properly on the client

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