GetField | Documentation

Index

Returns the value of a specified field from a document. If you don't specify an object, $getField returns the value of the field from $$CURRENT.

version: 4.4.2
see: https://docs.mongodb.com/manual/reference/operator/aggregation/getField/#mongodb-expression-exp.-getField

field: StringExpression<string>

Field in the input object for which you want to return a value. field can be any valid expression that resolves to a string constant.
Optional input?: string | ArrayElemAt | <internal>.Expression.First | <internal>.Expression.Last | Reduce | Literal | Function | MergeObjects | SetField | UnsetField | DateToParts | RegexFind

A valid expression that contains the field for which you want to return a value. input must resolve to an object, missing, null, or undefined. If omitted, defaults to the document currently being processed in the pipeline ($$CURRENT).