JSONata query to flatten array of arrays

Question

The JSONata doc "top-level-arrays-nested-arrays-and-array-flattening" covers the "flatten" case of an array of objects, each of which contains a property that contains an array value.

However, I have not been able to figure out how to flatten an array of arrays.

Q: What is the JSONata query to flatten an array of arrays?

input

    [ [1,2], [], [3] ]

desired

    [ 1, 2, 3 ]

Answer 1

I have figured out that flattening an array of arrays can be accomplished by using the $reduce function to iteratively apply the $append function.

    $reduce($, $append)

for this simple test case:

    $reduce( [ [1,2], [], [3] ], $append)

Q: Are there other ways to flatten an array of arrays in JSONata?