sumBy() function

返回对每个元素应用 f 后的值之和。空 iterable 返回 0。

Signature:

function sumBy<A>(f: (a: A) => number, iterable: Iterable<A>): number;
function sumBy<A>(
  f: (a: A) => number,
  iterable: AsyncIterable<A>,
): Promise<number>;

Example

sumBy(
  (a) => a.price,
  [
    { name: "apple", price: 100 },
    { name: "banana", price: 200 },
  ],
); // 300

sumBy((a) => a.price, []); // 0

pipe(
  [{ price: 100 }, { price: 200 }],
  sumBy((a) => a.price),
); // 300

Open Source Code