Function first

Produces a one-value iterable, with the first emitted value.

Without the optional predicate, it is the same as take(1).

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

const i = pipe(
    [10, 20, 30],
    first()
);

console.log(...i); //=> 10

console.log(i.first); //=> 10
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When the optional predicate is provided, the first value satisfying it will be emitted.

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

const i = pipe(
    [1, 2, 3, 4, 5],
    first(a => a % 2 === 0) // first even number
);

console.log(...i); //=> 2
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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.

See

• last
• take
• takeLast