Array Aggregation Operators¶

Name	Description
`$arrayElemAt`	Returns the element at the specified array index.
`$concatArrays`	Concatenates arrays to return the concatenated array.
`$filter`	Selects a subset of the array to return an array with only the elements that match the filter condition.
`$isArray`	Determines if the operand is an array. Returns a boolean.
`$size`	Returns the number of elements in the array. Accepts a single expression as argument.
`$slice`	Returns a subset of an array.