Function count

Goes through the entire iterable, counting the values, and produces a one-value iterable with the count.

import {pipe, count} from 'iter-ops';

const i = pipe(
    'hello world!',
    count()
);

console.log(...i); //=> 12

console.log(i.first); //=> 12
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When the optional predicate is specified, only values that satisfy the predicate are counted.

import {pipe, count} from 'iter-ops';

const i = pipe(
    'hello world!',
    count(a => a === 'l')
);

console.log(...i); //=> 3

console.log(i.first); //=> 3
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Note that the predicate can only return a Promise inside an asynchronous pipeline, or else the Promise will be treated as a truthy value.