const util = {
  // 创建一个a标签，并做下载点击事件
  downloadFile: function (blob, fileName) {
    if (window.navigator.msSaveOrOpenBlob) {
      // 兼容ie11
      try {
        window.navigator.msSaveOrOpenBlob(blob, fileName)
      } catch (e) {
        console.log(e)
      }
      return
    }
    const link = document.createElement('a')
    link.href = window.URL.createObjectURL(blob)
    link.download = fileName
    // 此写法兼容可火狐浏览器
    document.body.appendChild(link)
    const evt = document.createEvent('MouseEvents')
    evt.initEvent('click', false, false)
    link.dispatchEvent(evt)
    document.body.removeChild(link)
  },
  // 将Base64文件转为 Blob
  buildBlobByByte: function (data) {
    const raw = window.atob(data)
    const rawLength = raw.length
    const uInt8Array = new Uint8Array(rawLength)
    for (let i = 0; i < rawLength; ++i) {
      uInt8Array[i] = raw.charCodeAt(i)
    }
    return new Blob([uInt8Array])
  },
  // 二进制数组 生成文件
  downloadFileByByte: function (data, fileName) {
    const blob = this.buildBlobByByte(data)
    this.downloadFile(blob, fileName)
  }
}
export default util