js文件格式转换

1：base64转file文件流

let filename = 'filename' 
let bStr = atob(imgBase64Str) 
let n = bStr.length
let u8Arr = new Uint8Array(n)
let suffix = mime.split('/')[1]
while (n--) {
    u8Arr[n] = bStr.charCodeAt(n)
}
let files = new File([u8Arr], `${filename}.${suffix}`, {
    type: mime
})
files.uid = files.lastModified

后续追加file转base64以及文件压缩