How to convert Blob Url to Blob?

Question

I create blob to blob url using URL.createObjectURL. And how can i rechange it to blob.

    var blob = base64StringToBlob(b64Data, contentType);
    //Blob {size: 6474, type: 'image/jpeg'}size: 6474type: "image/jpeg"[[Prototype]]: Blob 
    var blobUrl = URL.createObjectURL(blob);
    //blob:http://localhost:4200/6b3cd400-5928-4cc8-9d13-3fb511a36ea0