Write a function of type String -> Integer. The input may or may not be a
valid JSON string. If it is valid, the resulting JavaScript value is expected
to be an object, but may not be. If it is an object, it is expected to have a
foo property whose value is expected to be an object, but may not be. This
value is expected to have a bar property which is expected to be an object
with a baz property whose value is expected to be an array of strings.
Each of these strings is expected to be a hex representation of an integer
(e.g. 0xFF). If every element of the array meets this expectation, the
function should return the sum of all the integers. Otherwise, the function
should return NaN. If any of the function's other expectations is not met,
the function should return NaN.
Here's a naive solution which only satisfies the "happy" path:
// f :: String -> Integer
const f = s =>
JSON.parse(s).foo.bar.baz.reduce((n, s) => n + parseInt(s, 16), 0);
f('{"foo":{"bar":{"baz":["0x0D","0x0E","0x0F"]}}}'); // => 42Here are some unhappy paths which should produce NaN:
f('[');
f('null');
f('{}');
f('{"foo":{}}');
f('{"foo":{"bar":{}}}');
f('{"foo":{"bar":{"baz":null}}}');
f('{"foo":{"bar":{"baz":[1,2,3]}}}');
f('{"foo":{"bar":{"baz":["foo","bar","baz"]}}}');
f('{"foo":{"bar":{"baz":["0x0D","0x0E","0x0F",null]}}}');