vue3使用el-upload

以下是使用Vue3和Element-UI的el-upload组件实现文件上传的示例代码：

1. 首先需要在Vue组件中引入el-upload组件和axios库：

<template>
  <el-upload
    class="upload-demo"
    action="/upload"
    :on-preview="handlePreview"
    :on-remove="handleRemove"
    :before-upload="beforeUpload"
    :on-success="handleSuccess"
    :on-error="handleError"
    :file-list="fileList"
    :auto-upload="false"
    :list-type="'picture-card'"
    :multiple="true"
    :limit="3"
    :on-exceed="handleExceed"
    :show-file-list="false">
    <i class="el-icon-plus"></i>
    <div class="el-upload__text">将文件拖到此处，或<em>点击上传</em></div>
    <div slot="tip" class="el-upload__tip">只能上传jpg/png文件，且不超过500kb</div>
  </el-upload>
</template>

<script>
import { ElUpload } from 'element-plus';
import axios from 'axios';

export default {
  components: {
    ElUpload,
  },
  data() {
    return {
      fileList: [],
    };
  },
  methods: {
    handlePreview(file) {
      console.log('预览文件', file);
    },
    handleRemove(file) {
      console.log('删除文件', file);
    },
    beforeUpload(file) {
      console.log('上传前处理', file);
    },
    handleSuccess(response, file, fileList) {
      console.log('上传成功', response, file, fileList);
    },
    handleError(error, file, fileList) {
      console.log('上传失败', error, file, fileList);
    },
    handleExceed(files, fileList) {
      console.log('超出文件个数限制', files, fileList);
    },
  },
};
</script>

2. 在Vue组件中实现上传文件的逻辑：

beforeUpload(file) {
  const isJPG = file.type === 'image/jpeg' || file.type === 'image/png';
  const isLt2M = file.size / 1024 / 1024 < 2;

  if (!isJPG) {
    this.$message.error('上传头像图片只能是 JPG/PNG 格式!');
    return false;
  }
  if (!isLt2M) {
    this.$message.error('上传头像图片大小不能超过 2MB!');
    return false;
  }

  const formData = new FormData();
  formData.append('file', file);

  axios.post('/api/upload', formData).then((response) => {
    this.fileList.push({
      name: file.name,
      url: response.data.url,
    });
  }).catch((error) => {
    console.log(error);
  });

  return false;
},

3. 在后端服务器中实现文件上传的逻辑：

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

const app = express();

const storage = multer.diskStorage({
  destination: (req, file, cb) => {
    cb(null, 'uploads/');
  },
  filename: (req, file, cb) => {
    const ext = path.extname(file.originalname);
    cb(null, `${Date.now()}${ext}`);
  },
});

const upload = multer({ storage });

app.post('/api/upload', upload.single('file'), (req, res) => {
  const file = req.file;
  const url = `http://localhost:3000/${file.path}`;

  res.json({ url });
});

app.listen(3000, () => {
  console.log('Server is running on port 3000');
});