Write a function fn that returns the length of an Array as Number.

Constraints:

• no use of length property
• size and length/size indicating properties of other data structures are also not allowed

Tips:

• try to avoid the comments section, as the solutions are often posted there
• it's way easier than you might think (which is why it's tagged #beginners)
• read about Array fundamentals
• don't expect the solution to be something that you should ever use in production code

Tests:

console.assert(fn([]) === 0)
console.assert(fn([1]) === 1)
console.assert(fn(['1']) === 1)
console.assert(fn(['1', 2, {}]) === 3)

Bonus:

This is all achievable by using 20 characters (inkl. function declaration) overall.