Find the maximum item of an array by given key

Return the record with the largest value in a field.

JavaScript Version 1.0.0 · MIT · .md

function maxBy({ values, key }) { return values.reduce((best, item) => (best === null || item[key] > best[key] ? item : best), null); }

Input & expected output

{
  "values": [
    {
      "recipient": "[email protected]",
      "attempts": 1
    },
    {
      "recipient": "[email protected]",
      "attempts": 3
    }
  ],
  "key": "attempts"
}

{
  "recipient": "[email protected]",
  "attempts": 3
}

The edge case

{
  "values": [],
  "key": "attempts"
}

null

Know the limits

• An empty array returns null; the original returned {}.
• The first record wins on ties.

The function above is the implementation used by the lab. The lab validates JSON types and caps size before execution; include equivalent validation when accepting untrusted input in your application.

Keep exploring

• Clone an array — Create a new array without copying the objects inside it.
• Remove duplicate values — Keep the first occurrence of each value, in its original order.
• Flatten a nested array — Turn a nested array into one sequence of values.