Why does setting XMLHttpRequest responseType before calling open throw?

Question

Running new XMLHttpRequest().responseType = \"json\" in the console throws an \"InvalidStateError\" exception in Firefox 26 and IE11 but not in Chrome 31.

Answer 1

It's a working draft, so it's normal if there are small differences or bugs in the implementations. I think Firefox still follows the behavior described in the draft of August 2011, where is specified that the exception is thrown if the state is not OPENED or HEADERS_RECEIVED.

Answer 2

Note that setting responseType after I call open on the xhr object solved my problem (using IE11)