String Operators

Operator	Description	Example
$concat	Concatenates two or more string properties or expressions in the passed in array.	{“$concat”: [“name.first”, {“$string”: “ ”}, “name.last”]}
$substr	Returns a portion of a string. Takes an array of three elements: source string, integer start index and integer length. The integer values can be literals, properties, or expressions.	{“$substr”: [“c_desc”, 0, 20]}
$toLower	Returns a lowercase version of the string argument.	{“$toLower”: “c_title”}
$toUpper	Returns an uppercase version of the string argument.	{“$toUpper”: “c_title”}
$strcasecmp	Performs a case-insensitive string comparison. Returns 0 if the two passed in array values are equivalent, 1 if the first value is greater than the second, -1 if the second value is greater than the first.	{“$strcasecmp”: [“name.first”, {“$string”: “J”}]}