base64转file二进制流文件

// base64图片转成二进制文件流
base64toFile(dataurl, filename = 'file') {
        let arr = dataurl.split(',')
        let mime = arr[0].match(/:(.*?);/)[1]
        let suffix = mime.split('/')[1]
        let bstr = atob(arr[1])
        let n = bstr.length
        let u8arr = new Uint8Array(n)
        while (n--) {
                u8arr[n] = bstr.charCodeAt(n)
        }
        return new File([u8arr], `${filename}.${suffix}`, {
                type: mime
        })
},