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https://github.com/n8brooks/generator_helpers
⚡ Synchronous generator monkey-patch for proposal-iterator-helpers written in TypeScript for Deno.
https://github.com/n8brooks/generator_helpers
deno iterator typescript
Last synced: 7 days ago
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⚡ Synchronous generator monkey-patch for proposal-iterator-helpers written in TypeScript for Deno.
- Host: GitHub
- URL: https://github.com/n8brooks/generator_helpers
- Owner: N8Brooks
- License: mit
- Created: 2021-10-02T18:20:35.000Z (about 3 years ago)
- Default Branch: main
- Last Pushed: 2024-10-15T19:10:57.000Z (2 months ago)
- Last Synced: 2024-12-17T16:13:51.483Z (9 days ago)
- Topics: deno, iterator, typescript
- Language: TypeScript
- Homepage: https://deno.land/x/generator_helpers
- Size: 58.6 KB
- Stars: 3
- Watchers: 1
- Forks: 0
- Open Issues: 2
-
Metadata Files:
- Readme: README.md
- License: LICENSE
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README
# generator_helpers
[](https://app.codecov.io/gh/N8Brooks/generator_helpers)
This module monkey patches
[proposal-iterator-helpers](https://github.com/tc39/proposal-iterator-helpers)
onto JavaScript or TypeScript generators. After importing this module, methods
that can normally only be used on arrays can also be used on generators. Methods
that take a function as an argument are given the `value` and `index` of
elements as parameters. A list of all monkey patched methods is provided below.
Check the proposal-iterator-helpers repository for more information and
examples.
- [`.map(mapperFn)`](https://github.com/tc39/proposal-iterator-helpers#mapmapperfn)
- [`.filter(filtererFn)`](https://github.com/tc39/proposal-iterator-helpers#filterfiltererfn)
- [`.take(limit)`](https://github.com/tc39/proposal-iterator-helpers#takelimit)
- [`.drop(limit)`](https://github.com/tc39/proposal-iterator-helpers#droplimit)
- [`.asIndexedPairs()`](https://github.com/tc39/proposal-iterator-helpers#asindexedpairs)
- [`.flatMap(mapperFn)`](https://github.com/tc39/proposal-iterator-helpers#flatmapmapperfn)
- [`.reduce(reducer [, initialValue ])`](https://github.com/tc39/proposal-iterator-helpers#reducereducer--initialvalue-)
- [`.toArray()`](https://github.com/tc39/proposal-iterator-helpers#toarray)
- [`.forEach(fn)`](https://github.com/tc39/proposal-iterator-helpers#foreachfn)
- [`.some(fn)`](https://github.com/tc39/proposal-iterator-helpers#somefn)
- [`.every(fn)`](https://github.com/tc39/proposal-iterator-helpers#everyfn)
- [`.find(fn)`](https://github.com/tc39/proposal-iterator-helpers#findfn)
Additionally `range` is provided as a helper generator as well as the
`Iterator.from` method.
- `range(stop)`
- `range(start, stop [, step = 1 ])`
- [`.from(object)`](https://github.com/tc39/proposal-iterator-helpers#fromobject)
## Examples
### `.map(mapperFn)` and `.toArray()`
The `.map(mapperFn)` method yields the results of `mapperFn` called with the
`value` and `index` of every element passed as parameters.
The `.toArray()` method returns the generator cast to an `Array`.
```ts
import "https://deno.land/x/generator_helpers/monkey_patch.ts";
import { assertEquals } from "https://deno.land/std/testing/asserts.ts";
function* lowercase(): Generator {
yield "a";
yield "b";
yield "c";
}
const uppercase = lowercase()
.map((char) => char.toUpperCase())
.toArray()
.join("");
assertEquals(uppercase, "ABC");
```
### `range(limit)` and `.reduce(reducer [, initialValue ])`
The `range(stop)` or `range(start, stop [, step = 1 ])` function is not included
in iterator-helpers proposal, but is included as a utility. It yields from `0`
up to, but not included, the `y0` parameter. If `y1` and `yd` are provided it
yields from `y0` until `y1` with steps of `yd`. The `yd` parameter is `1` by
default.
The `.reduce(reducer [, initialValue ])` method applies the `reducer` function
to each value using the previous result for for the first parameter. The first
time it is called `initialValue` is used if provided or else the first item of
the generator. The third parameter that is provided to `mapperFn` is the current
`index`.
```ts
import { range } from "https://deno.land/x/generator_helpers/monkey_patch.ts";
import { assertEquals } from "https://deno.land/std/testing/asserts.ts";
const sum = range(10).reduce((prev, cur) => prev + cur, 0);
assertEquals(sum, 45);
```
### `.flatMap(mapperFn)`
The `.flatMap(mapperFn)` method flattens the results from calls to `mapperFn`. Thereby
flattening the generator one level.
```ts
import { range } from "https://deno.land/x/generator_helpers/monkey_patch.ts";
import { assertEquals } from "https://deno.land/std/testing/asserts.ts";
const oneArray = range(5).flatMap((value) => Array(value).fill(value));
assertEquals(oneArray, [1, 2, 2, 3, 3, 3, 4, 4, 4, 4]);
```