Element提供了upload上传组件，可以查看官网upload组件的详细介绍；查看upload组件的上传源码upload/ajax，使用的是XHR对象上传文件。在项目实践中，发现该上传方法上传大文件时会出现问题，所以决定使用阿里云对象存储服务（Object Storage Service，简称OSS），OSS详细介绍可以查看官网，本文主要讲解的是OSS上传文件的前端，后台开发请查看官网介绍，SDK Browser.js讲解了前端如何进行上传。

1、使用npm安装SDK的开发包：

npm install ali-oss

2、OSS配置

let OSS = require('ali-oss');
let client= new OSS.Wrapper({
  accessKeyId: 'your access key',
  accessKeySecret: 'your access secret',
  bucket: 'your bucket name',
  region: 'oss-cn-hangzhou'
});

最新版的没有了Wrapper构造函数，直接配置

let oss = require('ali-oss');
var client = oss({
  accessKeyId: 'your access key',
  accessKeySecret: 'your access secret',
  bucket: 'your bucket name',
  region: 'oss-cn-hangzhou'
});

3、上传文件
  OSS上传文件分为上传Buffer内容、上传blob数据、分片上传，此处展示分片上传

let result = await client.multipartUpload('object-key', 'local-file', {
    progress: async function (p) {
      console.log('Progress: ' + p);
    }
  });

  js调用OSS上传文件已经没有问题，但是我们需要实现公用上传组件，Element UI已经实现了Upload上传组件，包括上传进度、异常处理、拖拽等；那我们还有必要重新开发一个像Upload一样的组件吗？通过查看Upload组件的API发现有一个http-request属性，http-request覆盖默认的上传行为，可以自定义上传的实现；看到这个我就省了很多事，直接用OSS上传覆盖XHR上传。代码如下：

<template>
  <div>
    <el-upload
      :auto-upload="false"
      :action="uploadUrl"
      ref="upload"
      :before-upload="fnBeforeUpload"
      :on-success="fnUploadSuccess"
      :on-exceed="fnUploadExceed"
      :data="data_extra"
      :headers="uploadHeaders"
      :http-request="fnUploadRequest"
      drag
      :limit="files"
      :disabled="disabled"
      multiple>
      <i class="el-icon-upload"></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">上传文件大小不能超过 1G</div>
    </el-upload>
  </div>
</template>
<script>
import UploadFileApi from '@/api/system/UploadFileApi'
import OSS from 'ali-oss'
export default {
  name: 'fileUpload',
  props: {
    data_extra: {
      type: Object,
      required: true
    },
    accept: {
      type: Array,
      required: true
    }
  },
  data () {
    return {
      uploadUrl: '',
      fileList: [],
      files: 10,
      uploadHeaders: {
        authorization: ''
      },
      disabled: false
    }
  },
  methods: {
    /**
     * @description [fnUploadRequest 覆盖默认的上传行为，实现自定义上传]
     * @author   shanshuizinong
     * @param    {object}   option [上传选项]
     * @return   {null}   [没有返回]
     */
    async fnUploadRequest (option) {
      try {
        let vm = this
        vm.disabled = true
        // 获取OSS配置信息
        let uploadFileApi = new UploadFileApi()
        let ret = await uploadFileApi.fileOssParams()
        if (!(ret.data && ret.data.code === '0' && ret.data.data)) {
          throw new Error('获取OSS参数失败')
        }
        let ossData = JSON.parse(ret.data.data)
        let relativePath = ossData.relativePath
        let client = new OSS.Wrapper({
          policy: ossData.policy,
          accessKeyId: ossData.accessid,
          accessKeySecret: ossData.accesssecret,
          bucket: ossData.bucket,
          signature: ossData.signature
        })
        let file = option.file
        const point = file.name.lastIndexOf('.')
        let suffix = file.name.substr(point)
        let fileName = file.name.substr(0, point)
        let date = vm.$moment().format('YYYYMMDDHHmm')
        let fileNames = `${fileName}_${date}${suffix}`
        // 分片上传文件
        ret = await client.multipartUpload(relativePath + fileNames, file, {
          progress: async function (p) {
            let e = {}
            e.percent = p * 100
            option.onProgress(e)
          }
        })
        console.log(ret)
        if (ret.res.statusCode === 200) {
          // option.onSuccess(ret)
          return ret
        } else {
          vm.disabled = false
          option.onError('上传失败')
        }
      } catch (error) {
        console.error(error)
        this.disabled = false
        option.onError('上传失败')
        this.$error(error.message)
      }
    },
    /**
     * @description [fnUploadSuccess 文件上传成功的函数]
     * @author   shanshuizinong
     * @return   {null}  [没有返回]
     */
    async fnUploadSuccess () {
      // TODO
    }
  }
}
</script>

  查看upload源码upload.vue知道httpRequest会有一个文件上传的option选项作为参数，upload/ajax源码中上传进度、上传成功、上传失败都是通过option调用其方法进行触发。