fyjson

Fast JSON parser for COM — yyjson engine exposed via IDispatch. Native C++, x86/x64.

Drop-in replacement for aspJSON and similar VBScript JSON parsers. Same API simplicity, 1000x faster.

Quick Start

Set fyj = CreateObject("fyjson")

' Parse
Set obj = fyj.Parse("{""name"":""Juan"",""age"":30,""tags"":[""a"",""b""]}")
name = obj("name")              ' "Juan"
obj("name") = "Pedro"           ' modify
obj("city") = "Córdoba"         ' add

' Create from scratch
Set obj = fyj.NewObject()
obj("id") = 1
obj("tags") = Array("a","b","c")  ' VBS Array → JSON array

' Arrays
Set arr = fyj.NewArray()
arr.Add "uno"
arr.Add 2
arr.Add Null

' Iterate
For Each key In obj
    WScript.Echo key & " = " & obj(key)
Next

' Nest objects
Set inner = fyj.NewObject()
inner("x") = 1
Set obj("nested") = inner

' Serialize
WScript.Echo obj.ToString()

API

Factory — CreateObject("fyjson")

Method	Returns	Description
Parse(jsonString)	JsonObject	Parse JSON string
NewObject()	JsonObject	Empty {}
NewArray()	JsonObject	Empty []

JsonObject — objects, arrays and values

Member	Type	Description
(key)	r/w	Get/set by key (objects), case-insensitive
(index)	r/w	Get/set by index (arrays)
Add(value)	method	Append to array
Add(key, value)	method	Add to object (Dictionary-compatible)
Remove(key|index)	method	Remove entry
Count	int	Number of keys/items
Exists(key)	bool	Key exists? (case-insensitive)
IsObject	bool	Is {}?
IsArray	bool	Is []?
IsNull	bool	Is null?
ToString()	string	Serialize to JSON
For Each	enum	Iterate keys (objects) or values (arrays)

Dictionary compatibility

Key lookup is case-insensitive, like Scripting.Dictionary with CompareMode = vbTextCompare. Original key casing is preserved in serialization.

Set obj = fyj.Parse("{""Name"":""Juan""}")
obj("name")    ' "Juan" — case-insensitive match
obj("NAME")    ' "Juan" — same
obj.ToString() ' {"Name":"Juan"} — original case preserved

Add(key, value) works like Dictionary's .Add:

Set obj = fyj.NewObject()
obj.Add "name", "Juan"
obj.Add "age", 30

Scripting.Dictionary objects passed as values are automatically converted to JSON objects, recursively:

Set dict = CreateObject("Scripting.Dictionary")
dict.Add "city", "Córdoba"
dict.Add "zip", "5000"

Set obj = fyj.NewObject()
obj.Add "address", dict       ' Dictionary → {"city":"Córdoba","zip":"5000"}
WScript.Echo obj.ToString()
' {"address":{"city":"Córdoba","zip":"5000"}}

This allows gradual migration from Dictionary-based code without rewriting payload construction.

Benchmark

Parsing + iterating search results (FluyeDoors, 2026-04-22):

Docs	JSON Size	aspJSON (VBS)	fyjson
100	14 KB	125 ms	0.1 ms
1,000	142 KB	7,941 ms	0.3 ms
15,000	5.4 MB	crash	7.7 ms

Install

:: Register (run as admin)
%SystemRoot%\System32\regsvr32 fyjson64.dll
%SystemRoot%\SysWOW64\regsvr32 fyjson32.dll

Build

Requires Visual Studio Build Tools with C++ and /std:c++17.

build64.bat
build32.bat

Compatibility

Windows 7+ / Windows Server 2008 R2+. Works with any COM client: VBScript, VBA, Classic ASP, JScript, WSH, PowerShell.

License

MIT — see LICENSE.

yyjson engine by ibireme (MIT).

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Jorge Pagano - Fluye