maxBy

Finds the first item with the largest finite derived number.

Code

maxBy.ts

export type MaxBySelector<Value> = (
  this: void,
  value: Value,
  index: number,
  array: readonly (Value | undefined)[],
) => number;

/** Returns the first value with the largest finite derived number. */
export const maxBy = <const T>(
  array: readonly T[],
  getValue: MaxBySelector<T>,
): T | undefined => {
  let result: T | undefined;
  let maximum = -Infinity;
  let hasResult = false;

  for (let index = 0; index < array.length; index += 1) {
    if (!Object.hasOwn(array, index)) continue;
    const value = array[index] as T;
    const candidate = getValue(value, index, array);
    if (!Number.isFinite(candidate)) continue;
    if (!hasResult || candidate > maximum) {
      result = value;
      maximum = candidate;
      hasResult = true;
    }
  }
  return result;
};

Download

wget

Terminal

wget -O src/lib/maxBy.ts https://raw.githubusercontent.com/jrTilak/lazykit/HEAD/registry/functions/maxBy.ts

degit

Terminal

temp_dir="$(mktemp -d)" && bunx degit jrTilak/lazykit/registry/functions "$temp_dir" && mv "$temp_dir/maxBy.ts" src/lib/maxBy.ts && rm -r "$temp_dir"

Examples

maxBy.example.ts

import { maxBy } from "./maxBy";

const highest = maxBy(
  [{ name: "A", score: 8 }, { name: "B", score: 10 }],
  (item) => item.score
);

Props

• array (readonly T[]) — Candidate values. Empty slots are skipped.
• getValue ((value: T, index, array: readonly (T | undefined)[]) => number) — Produces comparable numbers and is invoked without a receiver. value is always present; the original array retains skipped holes.
• Returns T | undefined; non-finite results are ignored.