I've read (here) that IE10 supports FormData(). But when I type this into the IE10 JavaScript console:
foo = new FormData();
I get the error, "FormData not defined"
Does IE10 support FormData() or doesn't it? Is there a trick to getting it to work in IE10?
I can confirm that it does - running your code in the console on this page works fine.
I will therefore hypothesize that you are in Quirks Mode, and therefore the browser is pretending it doesn't know it to be compatible with said Mode.
Make sure your page has a valid <!DOCTYPE html> at the start and no errors to fall back into quirks mode.
Also make sure your webserver request "edge" compatibility mode. That may help preventing fallback to older compatibility modes.
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