I have read this and this questions which seems to suggest that the file MIME type could be checked using javascript on client side. Now, I understand that the real validation still has to be done on server side. I want to perform a client side checking to avoid unnecessary wastage of server resource.
To test whether this can be done on client side, I changed the extension of a JPEG test file to .png and choose the file for upload. Before sending the file, I query the file object using a javascript console:
document.getElementsByTagName('input')[0].files[0];
This is what I get on Chrome 28.0:
File {webkitRelativePath: “”, lastModifiedDate: Tue Oct 16 2012
10:00:00 GMT+0000 (UTC), name: “test.png”, type: “image/png”, size:
500055…}
It shows type to be image/png which seems to indicate that the checking is done based on file extension instead of MIME type. I tried Firefox 22.0 and it gives me the same result. But according to the W3C spec, MIME Sniffing should be implemented.
Am I right to say that there is no way to check the MIME type with javascript at the moment? Or am I missing something?
