30-seconds-of-code/snippets/reduceWhich.md

title, tags, cover, firstSeen, lastUpdated

title	tags	cover	firstSeen	lastUpdated
Min and max of array based on provided function	array	blog_images/orange-coffee.jpg	2018-01-24T12:41:03+02:00	2020-11-03T22:11:18+02:00

Returns the minimum/maximum value of an array, after applying the provided function to set the comparing rule.

• Use Array.prototype.reduce() in combination with the comparator function to get the appropriate element in the array.
• Omit the second argument, comparator, to use the default one that returns the minimum element in the array.

const reduceWhich = (arr, comparator = (a, b) => a - b) =>
  arr.reduce((a, b) => (comparator(a, b) >= 0 ? b : a));

reduceWhich([1, 3, 2]); // 1
reduceWhich([1, 3, 2], (a, b) => b - a); // 3
reduceWhich(
  [
    { name: 'Tom', age: 12 },
    { name: 'Jack', age: 18 },
    { name: 'Lucy', age: 9 }
  ],
  (a, b) => a.age - b.age
); // {name: 'Lucy', age: 9}