JSON

require("internal.json") serializes Lua values to JSON and back. It is a built-in module, available in every script type. In JavaScript and TypeScript the module has encode and decode, and no to_array.

local json = require("internal.json")

json.encode(value)

local str = json.encode({ key = "value", items = { 1, 2, 3 } })
-- '{"key":"value","items":[1,2,3]}'

Converts a Lua value to a JSON string. A table whose length (#) is greater than 0 encodes as an array of its elements 1 to that length, and any other keys it has are left out. A table of length 0 encodes as an object, and raises if a key is not a string. A table marked with to_array, or an array that came from JSON, always encodes as an array.

json.decode(string)

local tbl = json.decode('{"key": "value"}')
-- tbl.key == "value"

Parses a JSON string into a Lua value. Raises when the input is not valid JSON. A JSON null decodes to a sentinel value rather than nil: the sentinel is truthy, and it encodes back to null. A decoded array keeps its array marking, so emptying it still encodes as [].

json.to_array(table)

return { items = json.to_array(results) }
-- With results:    {"items": [{"name": "a"}, {"name": "b"}]}
-- Without results: {"items": []}

Returns a copy of the table’s elements 1 to its length, marked so it always encodes as a JSON array. The table you pass is left as it was, so use the returned one. Lua does not distinguish an empty array from an empty object, so an empty {} encodes as {} unless it is marked. Pages and record lists returned by a library are already marked. Mark a table you build yourself with table.insert or index assignment, whether it is returned from handle or passed to json.encode.