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.
From MongoDB 4.0, you can use the $toLong aggregation pipeline operator to convert a value to a long.
From MongoDB 4.0, you can use the $toInt aggregation pipeline operator to convert a value to an integer.
From MongoDB 4.0, you can use the $toDouble aggregation pipeline operator to convert a value to a double.
From MongoDB 4.0, you can use the $toDecimal aggregation pipeline operator to convert a value to a decimal.
From MongoDB 4.0, you can use the $toBool aggregation pipeline operator to convert a value to a boolean.
From MongoDB 4.0, you can use the $toString aggregation pipeline operator to convert a value to a string.
In MongoDB, you can use the $convert aggregation pipeline operator to convert a value to a specified type.
You can convert any valid expression to a double, string, ObjectId, boolean, Date, integer, long, or decimal.
In MongoDB, the Date() method returns a date either as a string or as a Date object.
Date(), it returns the current date as a string in the mongo shell.new Date(), it returns the current date as a Date object. You can also provide a specific date as an argument to new Date(), so that it uses that date.
MongoDB provides the NOW system variable that allows you to get the current datetime value when using an aggregation pipeline.
This can be useful for when you want to update a document with the current datetime.