The exists method checks whether a specified path exists in the JSON value.
exists( pathElements )
| Argument | Description | 
|---|---|
| pathElements | (json_path_string_or_integer) The path to check. Specify one or more path elements, which might be object attribute names (strings) or array indexes (integers). | 
(Boolean) Returns true if the path exists, false otherwise.
Consider the following JSON:
{
  "product": "IDOL",
  "component": "CFS",
  "version": { "major": 11, "minor": 3 },
  "ports": [
    { "type": "ACI", "number": 7000 },
    { "type": "Service", "number": 17000 }
  ]
}
        If this JSON is represented by a LuaJsonValue object named myJsonValue, you could use the exists method as follows:
print (myJsonValue:exists("ports",0,"type"))
-- true (LuaJsonArrays are zero-indexed)
print (myJsonValue:exists("ports",2,"type"))
-- false (LuaJsonArrays are zero-indexed, and there is no third value)
print (myJsonValue:exists("version", "major"))
-- true
        |  |