js 发送文件大小

document.getElementById('fileInput').addEventListener('change', function(event) {
    const file = event.target.files[0];
    const maxSize = 5 * 1024 * 1024; // 5MB
    if (file.size > maxSize) {
        alert('文件大小不能超过5MB');
        event.target.value = ''; // 清空文件输入
    }
});

const express = require('express');
const multer = require('multer');
const app = express();

const upload = multer({
    limits: { fileSize: 5 * 1024 * 1024 } // 5MB
});

app.post('/upload', upload.single('file'), (req, res) => {
    res.send('文件上传成功');
});

app.use((err, req, res, next) => {
    if (err.code === 'LIMIT_FILE_SIZE') {
        res.status(400).send('文件大小不能超过5MB');
    } else {
        next(err);
    }
});

app.listen(3000, () => {
    console.log('服务器运行在 http://localhost:3000');
});