【Node.js】大文件上传（分片上传）

在Node.js中实现大文件的分片上传，你可以使用以下步骤：

1. 前端将文件分割成多个分片。
2. 逐个上传分片到服务器。
3. 服务器端接收分片并暂存，最后合并分片为原文件。

以下是实现分片上传的示例代码：

前端（HTML + JavaScript）

<form id="uploadForm">
  <input type="file" id="file" name="file"/>
  <button type="button" onclick="uploadFile()">Upload</button>
</form>
 
<script>
function uploadFile() {
  const file = document.getElementById('file').files[0];
  const chunkSize = 1024 * 1024; // 每个分片的大小，这里以1MB为例
  const totalChunks = Math.ceil(file.size / chunkSize);
 
  for (let i = 0; i < totalChunks; i++) {
    const chunk = file.slice(chunkSize * i, i === totalChunks - 1 ? file.size : chunkSize * (i + 1));
    const formData = new FormData();
    formData.append('chunk', chunk);
    formData.append('filename', file.name);
    formData.append('chunkedIndex', i);
    formData.append('totalChunks', totalChunks);
 
    fetch('/upload', {
      method: 'POST',
      body: formData
    })
    .then(response => response.json())
    .then(data => console.log(data));
  }
}
</script>

服务端（Node.js + Express）

const express = require('express');
const fs = require('fs');
const path = require('path');
const app = express();
const port = 3000;
 
app.use(express.json());
app.use(express.static('public'));
 
app.post('/upload', (req, res) => {
  const filename = req.body.filename;
  const chunkedIndex = req.body.chunkedIndex;
  const totalChunks = req.body.totalChunks;
  const chunk = req.body.chunk;
  const filePath = path.join(__dirname, 'public', filename);
  const writeStream = fs.createWriteStream(filePath, { flags: 'r+' });
 
  writeStream.on('open', () => {
    writeStream.write(chunk, {
      encoding: 'base64',
      position: chunkedIndex * chunk.length
    });
    writeStream.close();
    res.json({ status: 'Chunk uploaded successfully', chunkedIndex });
  });
 
  writeStream.on('error', (err) => {
    console.error(err);
    res.status(500).json({ error: 'Error writing to file' });
  });
 
  writeStream.on('finish', () => {
    if (chunkedIndex === totalChunks - 1) {
      console.log('Upload completed