Comment by zzo38computer

It depends what you intend to do with the parsed data, and where the input comes from and where the output will be going to. There are situations that allocations can be reduced or avoided, but that is not all of them. (In some cases, you do not need full parsing, e.g. to split an array, you can check if it is a string or not and the nesting level, and then find the commas outside of any arrays other than the first one, to be split.) (If the input is in memory, then you can also consider if you can modify that memory for parsing, which is sometimes suitable but sometimes not.)

However, for many applications, it will be better to use a binary format (or in some cases, a different text format) rather than JSON or XML.

(For the PostScript binary format, there is no escaping, and the structure does not need to be parsed and converted ahead of time; items in an array are consecutive and fixed size, and data it references (strings and other arrays) is given by an offset, so you can avoid most of the parsing. However, note that key/value lists in PostScript binary format is nonstandard (even though PostScript does have that type, it does not have a standard representation in the binary object format), and that PostScript has a better string type than JavaScript but a worse numeric type than JavaScript.)