用vuejs写一个断点续传的功能

可以的，具体实现需要使用 axios 库配合后台接口实现文件上传与下载功能，在前端使用 Vue.js 实现进度条与断点续传的逻辑。以下是大致的代码示例：

template:

<template>
  <div>
    <h3>文件上传</h3>
    <input type="file" @change="handleFileChange" />
    <button @click="uploadFile">上传</button>
    <h3>文件下载</h3>
    <input type="text" v-model="fileName" placeholder="请填写文件名" />
    <button @click="downloadFile">下载</button>
    <div v-if="showProgress" style="margin-top: 20px;">
      <p>上传/下载进度：{{ progress }}%</p>
      <progress :value="progress" max="100"></progress>
    </div>
  </div>
</template>

script：

<script>
import axios from 'axios'

export default {
  data () {
    return {
      file: null,
      showProgress: false,
      progress: 0,
      fileName: ''
    }
  },
  methods: {
    handleFileChange (event) {
      this.file = event.target.files[0]
    },
    uploadFile () {
      const formData = new FormData()
      formData.append('file', this.file)
      axios.post('/api/upload', formData, {
        headers: {
          'Content-Type': 'multipart/form-data'
        },
        onUploadProgress: (progressEvent) => {
          this.progress = parseInt(Math.round((progressEvent.loaded / progressEvent.total) * 100))
          this.showProgress = true
        }
      })
      .then(response => {
        console.log(`上传成功！文件地址为：${response.data}`)
      })
      .catch(error => {
        console.log(error)
      })
    },
    downloadFile () {
      axios({
        url: `/api/download/${this.fileName}`,
        method: 'GET',
        responseType: 'blob',
        onDownloadProgress: (progressEvent) => {
          this.progress = parseInt(Math.round((progressEvent.loaded / progressEvent.total) * 100))
          this.showProgress = true
        }
      })
      .then(response => {
        const url = window.URL.createObjectURL(new Blob([response.data]))
        const link = document.createElement('a')
        link.href = url
        link.setAttribute('download', `${this.fileName}`)
        document.body.appendChild(link)
        link.click()
      })
      .catch(error => {
        console.log(error)
      })
    }
  }
}
</script>

注意：上述代码仅供参考，实际情况中需要根据自己的需求进行调整。