If you have documents that store dates as Date objects, but you want to return them in a different format, you can use the $dateToString aggregate pipeline operator.
For example, you might want a date to be returned in mm/dd/yyyy format instead of the long ISODate() format that includes minutes, seconds, milliseconds, etc
The $dateToString operator converts the Date object to a string, and optionally allows you to specify a format for the resulting output.
In MongoDB, the $sort aggregation pipeline stage sorts all input documents and returns them to the pipeline in sorted order.
In MongoDB, the $switch aggregation pipeline operator evaluates a series of case expressions, and executes a specified expression only when a case expression evaluates to true.
In MongoDB, the $mergeObjects aggregation pipeline operator combines multiple documents into a single document.
In MongoDB you can use the $isArray aggregation pipeline operator to check whether or not a value is an array.
It accepts any valid expression, and returns true if the expression is an array, false if it’s not.
In MongoDB, the $literal aggregation pipeline operator returns a value without parsing.
It accepts any valid expression, and returns the unparsed expression.
The $literal operator can be useful for when you have a value that MongoDB could inadvertently interpret as an expression, but you don’t want it to.
For example, if you have a monetary amount that includes a dollar sign, MongoDB might inadvertently interpret that as a field name. You can use $literal to prevent MongoDB from interpreting such expressions.
In MongoDB, the $ln aggregation pipeline operator calculates the natural logarithm (ln) of a number and returns the result as a double.
In MongoDB, the $log aggregation pipeline operator calculates the log of a number in the specified base and returns the result as a double.
In MongoDB, the $indexOfCP aggregation pipeline operator searches a string for an occurrence of a substring and returns the UTF code point index of the first occurrence.
The UTF code point index is zero-based (i.e. it starts at 0).
In MongoDB, the $indexOfBytes aggregation pipeline operator searches a string for an occurrence of a substring and returns the UTF-8 byte index of the first occurrence.
The UTF byte index is zero-based (i.e. it starts at 0).