How to give a Blob uploaded as FormData a file name

Question

I am currently uploading images pasted from the clipboard with the following code      Turns out getAsFile will return a blob  not a file var blob   event clipboardData items 0  getAsFile         form   new FormData        request   new XMLHttpRequest    form append  blob  blob   request open               POST                 upload               true            request send form     Turns out the uploaded form field with receive a name similar to this  Blob157fce71535b4f93ba92ac6053d81e3a  Is there any way to set this or receive this file name client side  without doing any server side communication

User · Answer

It really depends on how the server on the other side is configured and with what modules for how it handles a blob post   You can try putting the desired name in the path for your post    request open       POST         upload myname bmp       true

User · Answer

That name looks derived from an object URL GUID  Do the following to get the object URL that the name was derived from   var URL   self URL    self webkitURL    self  var object url   URL createObjectURL blob   URL revokeObjectURL object url     object url will be formatted as blob  origin  GUID  in Google Chrome and moz-filedata  GUID  in Firefox  An origin is the protocol host non-standard port for the protocol  For example  blob http   stackoverflow com e7bc644d-d174-4d5e-b85d-beeb89c17743 or blob http      1  123 15111656-e46c-411d-a697-a09d23ec9a99  You probably want to extract the GUID and strip any dashes

User · Answer

Are you using Google App Engine  You could use cookies  made with JavaScript  to maintain a relationship between filenames and the name received from the server

User · Answer

For Chrome  Safari and Firefox  just use this   form append  blob   blob  filename      see MDN documentation

User · Answer

When you are using Google Chrome you can use abuse the Google Filesystem API for this  Here you can create a file with a specified name and write the content of a blob to it  Then you can return the result to the user   I have not found a good way for Firefox yet  probably a small piece of Flash like downloadify is required to name a blob   IE10 has a msSaveBlob   function in the BlobBuilder    Maybe this is more for downloading a blob  but it is related

User · Answer

Adding this here as it doesn t seem to be here   Aside from the excellent solution of form append  blob  blob  filename   you can also turn the blob into a File instance   var blob   new Blob  JSON stringify  0 1 2      type    application json     var fileOfBlob   new File  blob    aFileName json    form append  upload   fileOfBlob

User · Answer

Since you re getting the data pasted to clipboard  there is no reliable way of knowing the origin of the file and its properties  including name     Your best bet is to come up with a file naming scheme of your own and send along with the blob   form append  filename  getFileName     form append  blob  blob    function getFileName         logic to generate file names

User · Answer

Haven t tested it  but that should alert the blobs data url   var blob   event clipboardData items 0  getAsFile         form   new FormData        request   new XMLHttpRequest     var reader   new FileReader    reader onload   function event      alert event target result       lt -- data url    reader readAsDataURL blob

[javascript] How to give a Blob uploaded as FormData a file name?

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