From MongoDB 4.0, you can use the $toObjectId aggregation pipeline operator to convert a string to an ObjectId.
The string must be a hexadecimal string of length 24.
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MongoDB $rtrim
In MongoDB, the $rtrim aggregation pipeline operator removes whitespace from the end of a string. This includes the null character.
It can also remove any character specified. For example, you could use it to remove all periods (.), exclamation marks (!), etc from the end of a string.
MongoDB $ltrim
In MongoDB, the $ltrim aggregation pipeline operator removes whitespace from the beginning of a string. This includes the null character.
It can also remove any character specified. For example, you could use it to remove all hyphen characters (-) from the beginning of a string.
MongoDB $trim
In MongoDB, the $trim aggregation pipeline operator removes whitespace from the beginning and end of a string. This includes the null character.
It can also remove any character specified. For example, you could use it to remove all hyphen characters (-) or periods (.) or all s characters, etc.
MongoDB Whitespace Characters
The following table contains a list of whitespace characters that MongoDB removes by default when using the $trim, $ltrim, and $rtrim aggregation pipeline operators.
MongoDB $toLong
From MongoDB 4.0, you can use the $toLong aggregation pipeline operator to convert a value to a long.
MongoDB $toInt
From MongoDB 4.0, you can use the $toInt aggregation pipeline operator to convert a value to an integer.
MongoDB $toDouble
From MongoDB 4.0, you can use the $toDouble aggregation pipeline operator to convert a value to a double.
MongoDB $toDecimal
From MongoDB 4.0, you can use the $toDecimal aggregation pipeline operator to convert a value to a decimal.
MongoDB $toBool
From MongoDB 4.0, you can use the $toBool aggregation pipeline operator to convert a value to a boolean.