QGIS/resources/function_help/json/to_json

{
  "name": "to_json",
  "type": "function",
  "description": "Create a JSON formatted string from a map, array or other value.",
  "arguments": [
    {"arg":"value", "description":"The input value"}],
  "examples": [
    { "expression":"to_json(map('qgis','rocks'))", "returns":"{\"qgis\":\"rocks\"}"},
    { "expression":"to_json(array(1,2,3))", "returns":"[1,2,3]"}
  ]
}