响应（response）助手函数

The Server Response object , (often abbreviated as res) includes a set of Express.js-like helper methods to improve the developer experience and increase the speed of creating new API endpoints.

The included helpers are:

• res.status(code)- A function to set the status code. codemust be a valid HTTP status code
• res.json(body)- Sends a JSON response. bodymust be a serializable object
• res.send(body)- Sends the HTTP response. bodycan be a string, an objector a Buffer
• res.redirect([status,] path)- Redirects to a specified path or URL. statusmust be a valid HTTP status code . If not specified, statusdefaults to "307" "Temporary redirect".

Setting the status code of a response

When sending a response back to the client, you can set the status code of the response.

The following example sets the status code of the response to 200(OK) and returns a messageproperty with the value of Hello from Next.js!as a JSON response:

export default function handler(req, res) {
  res.status(200).json({ message: 'Hello from Next.js!' })
}

Sending a JSON response

When sending a response back to the client you can send a JSON response, this must be a serializable object . In a real world application you might want to let the client know the status of the request depending on the result of the requested endpoint.

The following example sends a JSON response with the status code 200(OK) and the result of the async operation. It's contained in a try catch block to handle any errors that may occur, with the appropriate status code and error message caught and sent back to the client:

export default async function handler(req, res) {
  try {
    const result = await someAsyncOperation()
    res.status(200).json({ result })
  } catch (err) {
    res.status(500).json({ error: 'failed to load data' })
  }
}

Sending a HTTP response

Sending an HTTP response works the same way as when sending a JSON response. The only difference is that the response body can be a string, an objector a Buffer.

The following example sends a HTTP response with the status code 200(OK) and the result of the async operation.

export default async function handler(req, res) {
  try {
    const result = await someAsyncOperation()
    res.status(200).send({ result })
  } catch (err) {
    res.status(500).send({ error: 'failed to fetch data' })
  }
}

Redirects to a specified path or URL

Taking a form as an example, you may want to redirect your client to a specified path or URL once they have submitted the form.

The following example redirects the client to the /path if the form is successfully submitted:

export default async function handler(req, res) {
  const { name, message } = req.body
  try {
    await handleFormInputAsync({ name, message })
    res.redirect(307, '/')
  } catch (err) {
    res.status(500).send({ error: 'failed to fetch data' })
  }
}

Adding TypeScript types

You can make your response handlers more type-safe by importing the NextApiRequestand NextApiResponsetypes from next, in addition to those, you can also type your response data:

import type { NextApiRequest, NextApiResponse } from 'next'

type ResponseData = {
  message: string
}

export default function handler(
  req: NextApiRequest,
  res: NextApiResponse<ResponseData>
) {
  res.status(200).json({ message: 'Hello from Next.js!' })
}

To view more examples using types, check out the TypeScript documentation .

If you prefer to view your examples within a real projects structure you can checkout our examples repository:

• Basic API Routes
• API Routes with REST