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maxBy()

maxBy<T>(array, iteratee): T

maxBy<T>(array, iteratee): T | undefined

Returns the element with the maximum value computed by iteratee.

Type Parameters​

T: T​

The type of elements in the array.

Parameters​

Overload 1:

array: readonly [T, T]​

The array to iterate over.

iteratee: (value) => number​

A function that returns the value to compare.

Overload 2:

array: readonly T[]​

The array to iterate over.

iteratee: (value) => number​

A function that returns the value to compare.

Returns: T​

The element with the maximum value, or undefined if empty.

Since​

2.0.0

Performance​

O(n) time, O(1) space.

Also known as​

max (Radashi) · maxBy (Lodash, es-toolkit, Remeda, Ramda) · ❌ (Effect, Modern Dash, Antfu)

Example​

maxBy([{ name: 'John', age: 25 }, { name: 'Jane', age: 30 }] as const, (u) => u.age);
// => { name: 'Jane', age: 30 }

maxBy([{ name: 'John', age: 25 }, { name: 'Jane', age: 30 }], (u) => u.age);
// => { name: 'Jane', age: 30 }

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

How it works?​

Finds the element with the maximum value computed by iteratee.

Use Cases​

Find the highest-earning employee 📌​

Identify top performers by a numeric field. Perfect for HR analytics, leaderboards, or compensation reports.

const employees = [
  { name: "Alice", salary: 95000 },
  { name: "Bob", salary: 78000 },
  { name: "Charlie", salary: 120000 },
];

const highestPaid = maxBy(employees, (e) => e.salary);
// => { name: "Charlie", salary: 120000 }

Get the most recent entry​

Find the latest item based on timestamp or date. Ideal for activity feeds, audit logs, or "last updated" features.

const orders = [
  { id: "ORD-001", createdAt: new Date("2024-01-10") },
  { id: "ORD-002", createdAt: new Date("2024-01-15") },
  { id: "ORD-003", createdAt: new Date("2024-01-12") },
];

const mostRecent = maxBy(orders, (o) => o.createdAt.getTime());
// => { id: "ORD-002", createdAt: Date("2024-01-15") }

Select the best-rated product​

Find top-rated items for recommendations or featured sections. Useful for e-commerce, reviews, or content curation.

const products = [
  { name: "ProBook", rating: 4.5 },
  { name: "UltraSlim", rating: 4.8 },
  { name: "GameMaster", rating: 4.6 },
];

const topRated = maxBy(products, (p) => p.rating);
// => { name: "UltraSlim", rating: 4.8 }

Find the most engaged user for analytics​

Identify the user with the highest engagement score. Essential for analytics dashboards and user segmentation.

const users = [
  { id: "u1", name: "Alice", sessions: 45, pageViews: 320 },
  { id: "u2", name: "Bob", sessions: 12, pageViews: 85 },
  { id: "u3", name: "Charlie", sessions: 67, pageViews: 510 },
];

const mostEngaged = maxBy(users, (u) => u.pageViews);
// => { id: "u3", name: "Charlie", sessions: 67, pageViews: 510 }

Find the heaviest bundle for optimization​

Identify the largest bundle chunk for code-splitting opportunities. Critical for build optimization and performance audits.

const bundles = [
  { name: "vendor.js", size: 245000, gzip: 78000 },
  { name: "app.js", size: 189000, gzip: 52000 },
  { name: "charts.js", size: 312000, gzip: 95000 },
];

const heaviest = maxBy(bundles, (b) => b.gzip);
// => { name: "charts.js", size: 312000, gzip: 95000 }
console.log(`Consider code-splitting: ${heaviest?.name}`);