docs/reference/compat/math/sumBy.md
::: warning Use sumBy from es-toolkit
This sumBy function works slowly due to iteratee function processing and type conversion.
Use the faster and more modern sumBy from es-toolkit instead.
:::
Adds values that meet a condition.
const total = sumBy(array, iteratee);
sumBy(array, iteratee)Adds the results of applying a function to each element in an array.
import { sumBy } from 'es-toolkit/compat';
// Number array
sumBy([1, 2, 3], value => value);
// Returns: 6
sumBy([1.5, 2.5, 3.5], value => Math.floor(value));
// Returns: 6 (1 + 2 + 3)
// Empty array
sumBy([], value => value);
// Returns: 0
sumBy(array)If no function is provided, it adds the array values directly.
import { sumBy } from 'es-toolkit/compat';
sumBy([1, 2, 3]);
// Returns: 6
sumBy([1n, 2n, 3n]);
// Returns: 6n
Add specific properties from object arrays.
import { sumBy } from 'es-toolkit/compat';
const people = [
{ name: 'John', age: 25 },
{ name: 'Jane', age: 30 },
{ name: 'Bob', age: 35 },
];
sumBy(people, person => person.age);
// Returns: 90
// Can also use property name
sumBy(people, 'age');
// Returns: 90
Concatenates strings as well.
import { sumBy } from 'es-toolkit/compat';
const items = [{ a: '1' }, { a: '2' }];
sumBy(items, obj => obj.a);
// Returns: '12'
Invalid values are ignored.
import { sumBy } from 'es-toolkit/compat';
sumBy([1, undefined, 2], value => value);
// Returns: 3 (undefined ignored)
sumBy(null);
// Returns: 0
sumBy(undefined);
// Returns: 0
array (ArrayLike<T> | null | undefined): The array to process.iteratee (((value: T) => number) | string, optional): The function or property name to apply to each element.(number): Returns the total sum of values that meet the condition.