Function sumBy

sumBy<T>(
selector: MapperFunction<T, number>,
): CollectorFunction<T, number | undefined>
Returns a collector that returns the sum of all entries in the Iterable based on the selector function.
Type Parameters
- T
  Type of items in the source.
Parameters
- selector: MapperFunction<T, number>
Returns CollectorFunction<T, number | undefined>
Collector that returns the sum of all entries in the Iterable based on the selector function.
Example
```
const result = sumBy((x) => x)([1, 2, 3]);
console.log(result); // 6
```
- Defined in collectors/sync/sumBy.ts:14