@wormss/fixtake

A utility to prevent Iterator.prototype.take() (and other consumers) from automatically closing your generators.

The Problem

In modern JavaScript, using the new Iterator helpers like .take(n) or using a break inside a for...of loop will automatically call .return() on the underlying generator. This makes it impossible to partially consume a generator and then continue using it elsewhere.

function* numbers() {
  yield 1; yield 2; yield 3;
}

const gen = numbers();
const taken = Array.from(gen.take(2)); // [1, 2]
// gen is now CLOSED because .take() called .return()
console.log(gen.next()); // { value: undefined, done: true }

The Solution

fixTake "fixes" the generator by hiding its .return() method from consumers while exposing it as .close() for when you actually want to terminate it manually.

import { fixTake } from '@wormss/fixtake';

function* numbers() {
  yield 1; yield 2; yield 3; yield 4;
}

const gen = fixTake(numbers());

const firstTwo = Array.from(gen.take(2)); // [1, 2]
// gen is STILL OPEN!
console.log(gen.next().value); // 3

const lastOne = Array.from(gen.take(1)); // [4]
// gen is still open (but exhausted)

Installation

npm install @wormss/fixtake

Usage

Basic Example

import { fixTake } from '@wormss/fixtake';

function* source() {
  yield 'a';
  yield 'b';
  yield 'c';
}

const gen = fixTake(source());

// This would normally close 'gen'
for (const item of gen.take(1)) {
  console.log(item); // 'a'
}

// But with fixTake, we can keep going!
console.log(gen.next().value); // 'b'

Manual Closing

If you need to trigger finally blocks or terminate the generator early, use the added .close() method:

const gen = fixTake(someGenerator());
// ... do work ...
gen.close(); // Equivalent to the original .return()

API

fixTake(generator)

• Arguments: A standard Generator object.
• Returns: A CloseableGenerator which is the same generator but with .return set to undefined and the original .return moved to .close.

License

ISC