Javascript：如何从HTML文件输入获取.tgz MIME类型？

Question

I am able to get most file MIME types by checking the file in a HTML file element, however when choosing a .tgz file I do not get a type.

Here is a jsfiddle showing the file type when a file is selected from the HTML file input: http://jsfiddle.net/chrisabrams/cTJKf/

Answer 1

According to the spec it's up to the browser to attempt to determine the content-type and if it fails, it should return an empty string.

type

The ASCII-encoded string in lower case representing the media type of the Blob , expressed as an RFC2046 MIME type [ RFC2046 ]. On getting, conforming user agents MUST return the MIME type of the Blob , if it is known. If conforming user agents cannot determine the media type of the Blob , they MUST return the empty string. A string is a valid MIME type if it matches the media-type token defined in section 3.7 "Media Types" of RFC 2616 [ HTTP ].

So whatever browser you're using doesn't recognise what a .tgz file is - this could vary both per-browser and also per-operating-system however.

I'm using Opera on Linux and it recognises .tgz but - for example - doesn't recognise .xcf

Answer 2

It's probably browser-dependent. It works for me in Opera, and gives application/x-gzip , but gives nothing in anything else. You could check it manually with e.target.files[0].value .