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If you want to start using it in your scripts right away, check out backport.dorder.js which backports the constant all the way to Warzone 3.1 Beta 1!
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Currently, the JS API will try and persist any global vars with the exception of functions, constants and JS API features. This causes all sorts of problems as I outlined in sessionStorage and localStorage.
To my utter amazement, it looks like the new data persistence approach will be very similar to my proposed solution - we'll be getting two new global objects (the names of them are still under discussion):
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