input上传文件的各种转换操作（一）

文件对象---->base64

base64 ---> blob

blob --- > flie

本地json文件 ---> 读取成json

指定url浏览器下载文件

import { getBase64, dataURLtoBlobs, blobToFile } from '@/utils/util.js'

本地json文件 ---> 读取成json

    geJsonData (file) {
      const __this = this
      var reader = new FileReader()// 新建一个FileReader
      reader.readAsText(file, 'UTF-8')// 读取文件
      reader.onload = function (evt) { // 读取完文件之后会回来这里
        var fileString = evt.target.result // 读取文件内容
        const jsonObj = JSON.parse(fileString)
        __this.actData[file.name] = jsonObj.animations
      }
    },

文件对象---->base64

// util.js

export function getBase64 (img, callback) {
  console.log('getBase64', img)
  const reader = new FileReader()
  reader.addEventListener('load', (e) => {
    callback(reader.result)
  })
  reader.readAsDataURL(img)
}


handleChange (info) {
    // 得到blob格式数据 上传
    getBase64(item.originFileObj, (result) => {
            __this.fileBlobObj[item.name] = dataURLtoBlobs(result)
            __this.postImage(item)
     })

}

base64 ---> blob

// 将base64转换为blob
export function dataURLtoBlobs (dataurl) {
  var arr = dataurl.split(',')
  var mime = arr[0].match(/:(.*?);/)[1]
  var bstr = atob(arr[1])
  var n = bstr.length
  var u8arr = new Uint8Array(n)
  while (n--) {
    u8arr[n] = bstr.charCodeAt(n)
  }
  return new Blob([u8arr], { type: mime })
}

blob --- > flie

// 将blob转换为file
export function blobToFile (theBlob, fileName) {
  theBlob.lastModifiedDate = new Date()
  theBlob.name = fileName
  return theBlob
}

4、下载

  function openDownloadDialog (url, saveName) {
    if (typeof url === 'object' && url instanceof Blob) {
      url = URL.createObjectURL(url)
    }
    var aLink = document.createElement('a')
    aLink.href = url
    aLink.download = saveName || ''
    var event
    if (window.MouseEvent) event = new MouseEvent('click')
    else {
      event = document.createEvent('MouseEvents')
      event.initMouseEvent('click', true, false, window, 0, 0, 0, 0, 0, false, false, false, false, 0, null)
    }
    aLink.dispatchEvent(event)
  }

  openDownloadDialog(sheet2blob(sheet), xmlName + '.xlsx')

5、