1、base64转file对象

let imageBase64
let blob = dataURLtoBlob(imageBase64)
let file = blobToFile(blob, Date.now() + '.png')

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

 blobToFile(theBlob, fileName) {
            theBlob.lastModifiedDate = new Date()  // 文件最后的修改日期
            theBlob.name = fileName                // 文件名
            return new File([theBlob], fileName, { type: theBlob.type, lastModified: Date.now() })
 }

2、