Max By

Requirements

• Implement maxBy(array, iteratee). The criterion may be a callback (value, index, originalArray) => number or a direct property key such as 'score'.
• Return the original item with the largest score, not the score itself. When scores tie, return the first matching item in input order.
• Return undefined for empty input and do not call the callback. Evaluate each item exactly once and pass its original index and array.
• Assume a dense array and a valid criterion producing finite numeric scores. Property-key criteria refer to a single property, not nested paths.
• Do not sort or mutate the array, clone the selected item, or change object identities. Propagate callback errors.

Examples

Input: maxBy([{ name: 'Ada', score: 8 }, { name: 'Lin', score: 5 }], 'score')
Output: { name: 'Ada', score: 8 }

Input: maxBy([-3, 2, -5], (value) => Math.abs(value))
Output: -5

Input: maxBy([], (value) => value)
Output: undefined