API / rxjs/operators

max

The Max operator operates on an Observable that emits numbers (or items that can be compared with a provided function), and when source Observable completes it emits a single item: the item with the largest value.

 max<T>(comparer?: (x: T, y: T) => number): MonoTypeOperatorFunction<T>

Parameters

comparer

Optional. Default is undefined.

Optional comparer function that it will use instead of its default to compare the value of two items.

Returns

MonoTypeOperatorFunction<T>: An Observable that emits item with the largest value.

Description

Examples

Get the maximal value of a series of numbers

import { of } from 'rxjs';
import { max } from 'rxjs/operators';

of(5, 4, 7, 2, 8).pipe(
  max(),
)
.subscribe(x => console.log(x)); // -> 8

Use a comparer function to get the maximal item

import { of } from 'rxjs';
import { max } from 'rxjs/operators';

interface Person {
  age: number,
  name: string
}
of<Person>(
  {age: 7, name: 'Foo'},
  {age: 5, name: 'Bar'},
  {age: 9, name: 'Beer'},
).pipe(
  max<Person>((a: Person, b: Person) => a.age < b.age ? -1 : 1),
)
.subscribe((x: Person) => console.log(x.name)); // -> 'Beer'

See Also