Code Editor (JavaScript)
print(ee.Array([1]).mask([0])); // []
print(ee.Array([1]).mask([1])); // [1]
print(ee.Array([0, 1, 2, 3]).mask([0, 4, -1, 1.2])); // [1,2,3]
print(ee.Array([[1, 2, 3, 4]]).mask([[0, 0, 0, 0]])); // [[]]
print(ee.Array([[1, 2, 3, 4]]).mask([[1, 0, 1, 1]])); // [[1,3,4]]
var array = ee.Array([[1], [2], [3], [4]]);
print(array.mask([[0], [0], [0], [0]])); // []
print(array.mask([[1], [0], [1], [1]])); // [[1],[3],[4]]
var empty = ee.Array([], ee.PixelType.int8());
print(empty.mask(empty)); // []