这个包实际上是著名的 expressjs multer v2.0.0-rc.4 原生包的一个分支。主要对于那些喜欢 promise 风格编程而不是中间件的开发人员来说会很有趣。此外，同样重要的是，这个包是用 typescript 编写的，因此其中的类型支持和上下文文档都是一流的。

安装

确保已安装 node.js >= v20.0.6。可以使用以下命令安装该软件包：

npm install @ts-stack/multer

用法

multer 返回一个具有四个属性的对象：formfields、file、files 和 groups。 formfields 对象包含表单文本字段的值，文件、文件或组对象包含通过表单上传的文件（作为可读流）。

以下示例使用 expressjs 只是为了简单起见。事实上，@ts-stack/multer 不返回中间件，因此对于 expressjs 来说不如原始模块方便。基本使用示例：

import { multer } from '@ts-stack/multer';
import express from 'express';
import { createwritestream } from 'node:fs';

// here `avatar`, `photos` and `gallery` - is the names of the field in the html form.
const multer = new multer({ limits: { filesize: '10mb' } });
const parseavatar = multer.single('avatar');
const parsephotos = multer.array('photos', 12);
const parsegroups = multer.groups([{ name: 'avatar', maxcount: 1 }, { name: 'gallery', maxcount: 8 }]);
const app = express();

app.post('/profile', async (req, res, next) => {
  const parsedform = await parseavatar(req, req.headers);
  // parsedform.file is the `avatar` file
  // parsedform.formfields will hold the text fields, if there were any
  const path = `uploaded-files/${parsedform.file.originalname}`;
  const writablestream = createwritestream(path);
  parsedform.file.stream.pipe(writablestream);
  // ...
});

app.post('/photos/upload', async (req, res, next) => {
  const parsedform = await parsephotos(req, req.headers);
  // parsedform.files is array of `photos` files
  // parsedform.formfields will contain the text fields, if there were any
  const promises: promise<void>[] = [];
  parsedform.files.foreach((file) =&gt; {
    const promise = new promise<void>((resolve, reject) =&gt; {
      const path = `uploaded-files/${file.originalname}`;
      const writablestream = createwritestream(path);
      file.stream.pipe(writablestream);
      writablestream.on('finish', resolve);
      writablestream.on('error', reject);
    });
    promises.push(promise);
  });

  await promise.all(promises);
  // ...
});

app.post('/cool-profile', async (req, res, next) =&gt; {
  const parsedform = await parsegroups(req, req.headers);
  // parsedform.groups is an object (string -&gt; array) where fieldname is the key, and the value is array of files
  //
  // e.g.
  //  parsedform.groups['avatar'][0] -&gt; file
  //  parsedform.groups['gallery'] -&gt; array
  //
  // parsedform.formfields will contain the text fields, if there were any
});
</void></void>

如果您需要处理纯文本的多部分表单，可以使用 .none() 方法，例如：

import { multer } from '@ts-stack/multer';
import express from 'express';

const parseformfields = new multer().none();
const app = express();

app.post('/profile', async (req, res, next) => {
  const parsedform = await parseformfields(req, req.headers);
  // parsedform.formfields contains the text fields
});

错误处理

这是错误代码列表：

const errormessages = new map<errormessagecode string>([
  ['client_aborted', 'client aborted'],
  ['limit_file_size', 'file too large'],
  ['limit_file_count', 'too many files'],
  ['limit_field_key', 'field name too long'],
  ['limit_field_value', 'field value too long'],
  ['limit_field_count', 'too many fields'],
  ['limit_unexpected_file', 'unexpected file field'],
]);
</errormessagecode>

您可以在 multererror#code 属性中看到这些错误代码：

import { Multer, MulterError, ErrorMessageCode } from '@ts-stack/multer';

// ...
try {
  const multer = new Multer().single('avatar');
  const parsedForm = await multer(req, req.headers);
  // ...
} catch (err) {
  if (err instanceof MulterError) {
    err.code // This property is of type ErrorMessageCode.
    // ...
  }
}