concat

{ $concat: [ <expression1>, <expression2>, ... ] }

Concatenates strings and returns the concatenated string.

For example:

{ $concat: [ "A", " - ", "B" ] }

ltrim

{ $ltrim: { input: <string>,  chars: <string> } }

Removes whitespace characters, including null, or the specified characters from the beginning of a string.

For example:

{ $ltrim: { input: " test " } }

regexFind

{ $regexFind: { input: <expression> , regex: <expression>, options: <expression> } }

Provides regular expression (regex) pattern matching capability in aggregation expressions. If a match is found, returns a document that contains information on the first match. If a match is not found, returns null.

For example:

{ $regexFind: { input: "$col", regex: /te/ } }

regexFindAll

{ $regexFindAll: { input: <expression> , regex: <expression>, options: <expression> } }

Provides regular expression (regex) pattern matching capability in aggregation expressions. The operator returns an array of documents that contains information on each match. If a match is not found, returns an empty array.

For example:

{ $regexFindAll: { input: "$col", regex: /te/ } }

regexMatch

{ $regexMatch: { input: <expression> , regex: <expression>, options: <expression> } }

Performs a regular expression (regex) pattern matching and returns:true if a match exists,false if a match doesn’t exist.

For example:

{ $regexMatch: { input: "$col", regex: /te/ } }

rtrim

{ $rtrim: { input: <string>,  chars: <string> } }

Removes whitespace characters, including null, or the specified characters from the end of a string.

For example:

{ $rtrim: { input: " test "} }

split

{ $split: [ <string expression>, <delimiter> ] }

Divides a string into an array of substrings based on a delimiter. $split removes the delimiter and returns the resulting substrings as elements of an array. If the delimiter is not found in the string, $split returns the original string as the only element of an array.

For example:

{ $split: [ "June-15-2013", "-" ] }

strcasecmp

{ $strcasecmp: [ <expression1>, <expression2> ] }

Performs case-insensitive comparison of two strings. Returns:1 if first string is "greater than" the second string,0 if the two strings are equal,-1 if the first string is "less than" the second string.

For example:

{ $strcasecmp: [ "$col", "test" ] }

strLenBytes

{ $strLenBytes: <string expression> }

Returns the number of UTF-8 encoded bytes in the specified string.

For example:

{ $strLenBytes: "abcde" }

strLenCP

{ $strLenCP: <string expression> }

Returns the number of UTF-8 values in the specified string.

For example:

{ $strLenCP: "abcde" }

substr

{ $substr: [ <string>, <start>, <length> ] }

Returns a substring of a string, starting at a specified index position and including the specified number of characters. The index is zero-based.

For example:

{ $substr: [ "test", 0, 2 ] }

substrBytes

{ $substrBytes: [ <string expression>, <byte index>, <byte count> ] }

Returns the substring of a string. The substring starts with the character at the specified UTF-8 byte index (zero-based) in the string and continues for the number of bytes specified.

For example:

{ $substrBytes: [ "abcde", 1, 2 ] }

substrCP

{ $substrCP: [ <string expression>, <code point index>, <code point count> ] }

Returns the substring of a string. The substring starts with the character at the specified UTF-8 code point (CP) index (zero-based) in the string for the number of code points specified.

For example:

{ $substrCP: [ "abcde", 1, 2 ] }

toLower

{ $toLower: <expression> }

Converts a string to lowercase, returning the result.

For example:

{ $toLower: "TEST" }

toUpper

{ $toUpper: <expression> }

Converts a string to uppercase, returning the result.

For example:

{ $toUpper: "test" }

trim

{ $trim: { input: <string>,  chars: <string> } }

Removes whitespace characters, including null, or the specified characters from the beginning and end of a string.

For example:

{ $trim: { input: " test " } }

type

{ $type: <expression> }

Returns a string that specifies the BSON type of the argument.

For example:

{ $type: "a" }