Write a function minBy(array, iteratee) that looks through an array and returns the element for which the provided iteratee function produces the smallest value.

⚠️ If the iteratee returns null or undefined for every element, the function should return undefined.

Examples:

minBy([2, 3, 1, 4], (num) => num); 
// => 1

minBy([{ n: 1 }, { n: 2 }], (o) => o.n); 
// => { n: 1 }

minBy([{ n: 1 }, { n: 2 }], (o) => o.m); 
// => undefined