Json ⊄ js
Perhaps more pervasive and despairingly problematic is number representation.  JSON only, per specification, supports arbitrary precision numeric representation.  However, Javascript is -- also per specification (as I understand it) -- entirely floating point.  That makes working with money in Javascript somewhat hazardous.  While there are various arbitrary precision libraries out there for Javascript to assuage this, the problem is most JSON-parsing routines will always force one through a floating point conversion anyway, so a loss of precision is more or less inevitable.<p>While swiftly coercing raw off-the-wire number representations to one's arbitrary precision library of choice can avoid most cases of noticeable accumulated error, it is irksome that the only way everyone seems to get by is by cross their fingers that any loss in precision caused by "JSON.parse" is meaningless to their application.<p>Or, the problem can be soundly avoided by using strings in the JSON payload, which is lame but effective and probably one's best practical choice.  It is clearly an example of corruption spreading from Javascript to an otherwise reasonable feature of the data representation format JSON.