Not sure what this could possibly have to do with floating point numbers, nor am I aware of any function that does what you're describing. Is this some kind of JavaScript quirky behavior because nothing about floating point numbers has anything to do with coercing strings.
I've definitely been bitten by similar (not identical) stuff. I've seen data serialized and sent over the wire by I-don't-know-what where several parsers can't correctly parse/serialize and end up with the same thing written back. Be it 32 bit float/64 bit float/string parsed as 32 bit float/string parsed as 64 bit float/string parsed as big decimals: I don't care, the fact is there are buggy serializers, buggy parsers, and even sometimes buggy parsers going into infinite loop (the JVM is famous for that: there was a bug where Double.parseDouble could be sent into an infinite loop by feeing it a carefully crafted string).
I think the lesson is rather: don't use text based protocols for data serialization if you care about precision. Such things should never happen with a binary protocol.
