As a few people have noticed, we took a small breaking change to the JsRT API between the Windows 8.1 Preview and Windows 8.1 RTM. The
JsCreateFunction API got an additional parameter that allows registering a piece of data (which can just be null) with the native callback which will be provided to the callback when it’s invoked. It’s a super-useful place to stash something like a “this” pointer for a C++ callback, which is why we added it before the concrete completely dried on the API. It does mean, though, that most applications compiled against the preview will break and need to be recompiled against RTM.
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