For AI agents: the complete documentation index is available at /llms.txt, the full documentation bundle is available at /llms-full.txt, and this page is available as Markdown at /reference/array/maxBy.md.
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    maxBy es-toolkit

    Returns the element with the maximum value from the array based on the value returned by the transformation function.

    const max = maxBy(items, getValue);

    Usage

    maxBy(items, getValue)

    Use maxBy when you want to transform elements in an array to numeric values using a transformation function and find the original element with the largest value. It returns undefined for an empty array.

    import { maxBy } from 'es-toolkit/array';

// Find the element with the maximum value for a specific property in an object array.
const people = [
  { name: 'john', age: 30 },
  { name: 'jane', age: 28 },
  { name: 'joe', age: 26 },
];
maxBy(people, person => person.age);
// Returns: { name: 'john', age: 30 }

// Find the element with the largest absolute value in a number array.
const numbers = [-10, -5, 0, 5, 15];
maxBy(numbers, x => Math.abs(x));
// Returns: 15

    It returns undefined for an empty array.

    import { maxBy } from 'es-toolkit/array';

maxBy([], x => x.value); // undefined

    Parameters

    itemsT[]required

    The array to find the element with the maximum value.

    getValue(element: T, index: number, array: readonly T[]) => numberrequired

    A function that transforms each element into a number. It receives the element, its index, and the array.

    Returns

    The element with the largest value returned by the transformation function. Returns undefined if the array is empty.

    T | undefined

    Examples

    // Using index parameter
const items = [{ value: 10 }, { value: 20 }, { value: 15 }];
maxBy(items, (item, index) => item.value + index);
// Returns: { value: 20 }

// Using array parameter
maxBy(items, (item, _index, array) => item.value * array.length);
// Returns: { value: 20 }
    Source: es-toolkit

    Re-exported verbatim from es-toolkit. Implementation, edge cases, and performance behavior are owned upstream. This page mirrors the documentation at the pinned version; the linked source is authoritative.