https://github.com/lideming/generator-ext

Array-like methods for generators.
https://github.com/lideming/generator-ext

extension generator javascript

Last synced: 18 days ago
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Array-like methods for generators.

• Host: GitHub
• URL: https://github.com/lideming/generator-ext
• Owner: lideming
• License: mit
• Created: 2022-04-22T02:11:28.000Z (over 2 years ago)
• Default Branch: master
• Last Pushed: 2022-04-22T02:25:50.000Z (over 2 years ago)
• Last Synced: 2024-11-08T06:06:19.605Z (2 months ago)
• Topics: extension, generator, javascript
• Language: JavaScript
• Homepage:
• Size: 3.91 KB
• Stars: 0
• Watchers: 1
• Forks: 0
• Open Issues: 0
• Metadata Files:
  • Readme: README.md
  • License: LICENSE

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README

        
# JS Generator Extension

Array-like methods for generators.

[![npm](https://img.shields.io/npm/v/generator-ext?color=blue)](https://www.npmjs.com/package/generator-ext)

## Background

In C# and Python, we can do some operations on an iterator and get chained generators.

Python Example

```python

(x * 10 for x in range(10) if x % 2 == 1)

# got a generator for [10, 30, 50, 70, 90]

```

C# Example (click to expand)

```csharp

Enumerable.Range(0, 10)

    .Where(x => x % 2 == 1)

    .Select(x => x * 10)

// got a iterator for [10, 30, 50, 70, 90]

// using LINQ extension methods

from x in Enumerable.Range(0, 10)

    where x % 2 == 1

    select x * 10

// the same, using LINQ query syntax

```

Currently, to do the same thing in JavaScript:

```javascript

new Array(10).fill(0).map((x, i) => i)

  .filter(x => x % 2 == 1)

  .map(x => x * 10)

```

There are a few disadvantages:

- `new Array(n).fill(...).map(...)` is too long and confusing

- 3 intermediate arrays are created (`new Array()`, the first `map()`, `filter()`)

## Getting Started

```bash

npm install generator-ext

```

```javascript

import { range } from "generator-ext";

[...range(10).filter(x => x % 2 == 1).map(x => x * 10)]

```

- We have `range()` to get a Python-like range generator

- We can call methods like `map()` on any generator, retuning chained generator

- They are just (chained) generators. We can call `toArray()` on the generator to get the result as array, without any intermediate arrays.

  - `[...generator]` also works.

## Methods for Generators

These methods are added to the prototype of [GeneratorFunction](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/GeneratorFunction):

- Array-like methods (`map`, `filter`, `flat`, `flatMap`, `reduce`)

    - are identical to Array builtins, excepts they return generators instead of arrays.

- `toArray` method

## `range` Generator Function

Generates a number sequences. It's similar to `range` in Python.

```javascript

range(10)

// generator for [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]

range(3, 10)

// generator for [3, 4, 5, 6, 7, 8, 9]

range(3, 10, 2)

// generator for [3, 5, 7, 9]

```