Function jsonArray( txt )

Description:
Converts the supplied string to a JSONArray which can be interrogated further. If the input string doesn't have the syntax of a JSON array, a zero-length JSONArray will be returned.

The JSON parsing is currently somewhat lenient, for instance allowing a comma before a closing square bracket.

Parameters:
txt (String)
string assumed to contain a JSON array
Return Value (JSONArray):
JSON array value on which further methods can be called
Signature:
JSONArray jsonArray(String)