如何在Dataweave 2中使用过滤器和映射

%dw 2.0
output application/json

var students = [
  {
    "name": "Alice",
    "age": 20
  },
  {
    "name": "Bob",
    "age": 17
  },
  {
    "name": "Charlie",
    "age": 19
  }
]

var filteredStudents = students filter ($.age > 18)

---
filteredStudents

%dw 2.0
output application/json

var students = [
  {
    "name": "Alice",
    "age": 20
  },
  {
    "name": "Bob",
    "age": 17
  },
  {
    "name": "Charlie",
    "age": 19
  }
]

var transformedStudents = students map {
  "fullName": $.name,
  "yearsOld": $.age
}

---
transformedStudents