54 lines
1.4 KiB
Plaintext
54 lines
1.4 KiB
Plaintext
import { reduce } from './reduce';
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import { MonoTypeOperatorFunction } from '../types';
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import { isFunction } from '../util/isFunction';
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/**
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* The Max operator operates on an Observable that emits numbers (or items that can be compared with a provided function),
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* and when source Observable completes it emits a single item: the item with the largest value.
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*
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* 
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*
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* ## Examples
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*
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* Get the maximal value of a series of numbers
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*
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* ```ts
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* import { of, max } from 'rxjs';
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*
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* of(5, 4, 7, 2, 8)
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* .pipe(max())
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* .subscribe(x => console.log(x));
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*
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* // Outputs
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* // 8
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* ```
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*
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* Use a comparer function to get the maximal item
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*
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* ```ts
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* import { of, max } from 'rxjs';
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*
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* of(
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* { age: 7, name: 'Foo' },
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* { age: 5, name: 'Bar' },
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* { age: 9, name: 'Beer' }
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* ).pipe(
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* max((a, b) => a.age < b.age ? -1 : 1)
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* )
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* .subscribe(x => console.log(x.name));
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*
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* // Outputs
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* // 'Beer'
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* ```
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*
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* @see {@link min}
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*
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* @param {Function} [comparer] - Optional comparer function that it will use instead of its default to compare the
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* value of two items.
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* @return A function that returns an Observable that emits item with the
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* largest value.
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*/
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export function max<T>(comparer?: (x: T, y: T) => number): MonoTypeOperatorFunction<T> {
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return reduce(isFunction(comparer) ? (x, y) => (comparer(x, y) > 0 ? x : y) : (x, y) => (x > y ? x : y));
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}
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