js base64图片转换成文件File

base64图片转换成文件的代码，特此记录一下

export function base64ToBinary(base64,fileName) {
    let arr = base64.split(',');
    let  mime = arr[0].match(/:(.*?);/)[1];
    let  bstr = atob(arr[1]);
    let  n = bstr.length;
    let  u8arr = new Uint8Array(n);
    while (n--) {
        u8arr[n] = bstr.charCodeAt(n);
    }
    let blob = new Blob([u8arr], { type: mime });
    let newFile = blobToFile(blob, fileName);
    let lastModified = new Date().getTime()
    return new File([newFile], fileName, {lastModified: lastModified});
}

function blobToFile(theBlob, fileName) {
    theBlob.lastModifiedDate = new Date();
    theBlob.name = fileName;
    return theBlob;
}