Created: 2008-09-26 04:40
Updated: 2019-02-16 23:24
License: other


JSON Parser/Constructor for Lua


Thomas Harning Jr.

Source code:

Bug reports:


Lua 5.1, 5.2, 5.3, LuaJIT 2.0, or LuaJIT 2.1 LPeg (Tested with 0.7, 0.8, 0.9, 0.10, 0.12rc2, 1.0.1) For regressionTest: lfs (Tested with 1.6.3)

For lunit-tests:

lunitx >= 0.8


LPeg 0.11 may not work - it crashed during my initial tests, it is not in the test matrix.

Lua versions tested recently:

  • Lua 5.1.5
  • Lua 5.2.4
  • Lua 5.3.4
  • LuaJIT-2.0.4
  • LuaJIT-2.1.0-beta2


All-but tests: MIT-style, See LICENSE for details tests/*: Public Domain / MIT - whichever is least restrictive

Module/Function overview:

json.encode (callable module referencing json.encode.encode)

encode ( value : ANY-valid )

Takes in a JSON-encodable value and returns the JSON-encoded text Valid input types:

  • table
  • array-like table (spec below)
  • string
  • number
  • boolean
  • 'null' - represented by json.util.null

Table keys (string,number,boolean) are encoded as strings, others are erroneus Table values are any valid input-type Array-like tables are converted into JSON arrays... Position 1 maps to JSON Array position 0

json.decode (callable module referencing json.decode.decode)

decode (data : string, strict : optional boolean)

Takes in a string of JSON data and converts it into a Lua object If 'strict' is set, then the strict JSON rule-set is used


Useful utilities


Reference value to represent 'null' in a well-defined way to allow for null values to be inserted into an array/table


Reference value to represent 'undefined' in a well-defined way to allow for undefined values to be inserted into an array/table.

IsArray (t : ANY)

Checks if the passed in object is a plain-old-array based on whether or not is has the LuaJSON array metatable attached or the custom __is_luajson_array metadata key stored.

InitArray(t: table)

Sets the 'array' marker metatable to guarantee the table is represented as a LuaJSON array type.

isCall (t : ANY)

Checks if the passed in object is a LuaJSON call object.

buildCall(name : string, ... parameters)

Builds a call object with the given name and set of parameters. The name is stored in the 'name' field and the parameters in the 'parameters' field as an array.

Additional Utilities

clone (t : table)

Shallow-clones a table by iterating using pairs and assigning.

___printValue (tab : ANY, name : string)

recursively prints out all object values - if duplicates found, reference printed

___merge (t : table, ... : tables)

Shallow-merges a sequence of tables onto table t by iterating over each using pairs and assigning.

Internal Utilities - Not to Use

decodeCall doOptionMerge


parsing test suite from JSON_checker project of No listed license for these files in their package.

Cookies help us deliver our services. By using our services, you agree to our use of cookies Learn more