javascript如何使用Blob对象下载文件

import axios from 'axios'
/**
* 从服务器下载excel
*/
function downloadExcel (settings) {
 const defaultOptions = {
  responseType: 'arraybuffer'
 }
 Object.assign(settings.options, defaultOptions)
 requestToResponse(settings).then(res => {
  const filename = decodeURI(res.headers['content-disposition'].split('filename=')[1])
  if ('download' in document.createElement('a')) {
   downloadFile(res.data, filename)
  } else {
   Message.error('浏览器不支持')
  }
 })
}
/**
* 发送http请求
* @param {Object} settings api参数
* @returns reponse
*/
function requestToResponse (settings) {
  const defaultParams = {
  timeout: 45000,
  headers: {
   'X-Requested-With': 'XMLHttpRequest',
   'Content-Type': 'application/json'
  },
  responseType: 'json',
  method: 'POST'
 }
 Object.assign(defaultParams, settings)
  return new Promise((resolve, reject) => {
  axios(defaultParams).then(res => {
   resolve(res)
  }).catch(err => {
   reject(err)
  })
 })
}
/**
* blob下载（兼容IE）
* @param {String} content 文件内容
* @param {String} filename 文件名
*/
function downloadFile (content, filename) {
 const blob = new Blob([content])
 // IE
 if (window.navigator && window.navigator.msSaveOrOpenBlob) {
  window.navigator.msSaveOrOpenBlob(blob, filename)
 } else {
  imatateDownloadByA(window.URL.createObjectURL(blob), filename)
 }
}
/**
* 通过a标签模拟下载
* @param {String} href
* @param {String} filename
*/
function imatateDownloadByA (href, filename) {
 const a = document.createElement('a')
 a.download = filename
 a.style.display = 'none'
 a.href = href
 document.body.appendChild(a)
 a.click()
 a.remove()
 window.URL.revokeObjectURL(href)
}

// 下载excel
downloadExcel({
  url: '/default/excel/export',
  responseType: 'arraybuffer'
})