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https://github.com/ugaya40/leseq

Lazy collection(lazy list) with high tree-shaking affinity and easy customization.
https://github.com/ugaya40/leseq

async-iterable collection iterable lazy-evaluation lazy-sequences lazylist tree-shakable typescript zero-dependency

Last synced: 22 days ago
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Lazy collection(lazy list) with high tree-shaking affinity and easy customization.

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[![npm version](https://badge.fury.io/js/leseq.svg)](https://badge.fury.io/js/leseq)



Lazy list(lazy list) with high tree-shaking affinity and easy customization.



# Features

- 🎁 **Lazy Collection**: The collections are only enumerated to the minimum necessary. Infinite sequences are supported.

- 🎄 **Tree-Shakeable**: Only the features you use will be bundled.

- 👻 **Async Iterator Support**: *Iterable* can also be seamlessly treated as *Async Iterator*.

- 📎 **Easy-Customization**: You can easily create the functions you need by yourself. [In this way.](https://ugaya40.github.io/leseq/create/)

- 🗂 **Rxjs-like Syntax**: To achieve tree-shaking, we use an [rxjs](https://rxjs.dev/)-like syntax.

- ✅ **Simple Equality Strategy**: It uses a simple [Equality Strategy](https://ugaya40.github.io/leseq/equality/).

- 💯 **All Typed**: The whole thing is written in TypeScript, which also provides completion for type conversion between operators.

- 💨 **No dependencies**



```typescript

import {from, map, take} from 'leseq';



const result1 = from([1,2,3,4,5]).pipe(

  map(i => i * i),

  take(3)

).toArray();



//result1: [1,4,9]

```

This is the result of [bundle visualizer](https://github.com/btd/rollup-plugin-visualizer) in the example above (1.21KB gzipped).






# Resource

- ### [Demo(StackBlitz)](https://stackblitz.com/edit/typescript-vygaa6?devtoolsheight=33&file=index.ts)



- ### [Docs](https://ugaya40.github.io/leseq/)



# Advanced

- #### [Create Original Functions](https://ugaya40.github.io/leseq/create/)



- #### [Equality Strategy](https://ugaya40.github.io/leseq/equality/)



- #### [Finalization, and Resource Management](https://ugaya40.github.io/leseq/finalize/)



# Getting Started

```

npm install leseq

```

If you are using Async Iterable and *"target "* in **tsconfig.json** is smaller than **"es2018"**, you must add **"ES2018.AsyncGenerator "** and **"ES2018.AsyncIterable "** in **tsconfig.json/lib** or the type will not display properly.

```json

{

  "compilerOptions": {

    "target": "es6",

    "lib": ["DOM", "ES6", "ES2018.AsyncGenerator", "ES2018.AsyncIterable"]

  }

}



```

## Iterable

```typescript

import {from, map, take, find, range, reverse, filter} from 'leseq';



const result1 = from([1,2,3,4,5]).pipe(

  map(i => i * i),

  take(3)

)



for (const one of result1) {

  console.log(one)

}



//result: 1

//result: 4

//result: 9



const result2 = from([1,2,3,4,5]).pipe(

  filter(i => i % 2 == 0)

).value(

  find(i => i > 2)

);



//result2: 4



//lazy

const result3 = range(1, 10000000).pipe(

  take(3),

  reverse(),

  map((i) => i * i)

).toArray();



//result3: [9,4,1]

```

## Async Iterable

```typescript

import {from, mapAsync, filterAsync, fromAsAsync, findAsync, asyncSeq} from 'leseq';



const sleep = (milliseconds: number) => new Promise(resolve => setTimeout(resolve,milliseconds));



//from iterable to async iterable.

const result1 = await from([1,2,3,4,5]).to(asyncSeq()).pipe(

  mapAsync(async i => {

    await sleep(1000);

    return i * i;

  }),

  filterAsync(async i => i % 2 == 0)

).toArrayAsync();



//5 seconds later... result1: [4,16]



const result2 = await fromAsAsync([1,2,3,4,5]).pipe(

  mapAsync(async i => {

    await sleep(1000);

    return i * i;

  }),

  filterAsync(async i => i % 2 == 0)

).valueAsync(findAsync());



//2 seconds later... result2: 4



const result3 = await fromConcatAsAsync([1,2],[3,4]).pipe(

  mapAsync(async i => {

    await sleep(1000);

    return i * i;

  }),

);



for await (const one of result3) {

  console.log(one);

}



//1 seconds later... result: 1

//2 seconds later... result: 4

//3 seconds later... result: 9

//4 seconds later... result: 16

```

# Usage



It is possible to generate sequences (Seq<T>/AsyncSeq<T> object) with **Generator**, convert them to sequences with different characteristics with **To**, perform operations such as value conversion and filtering with any number of **Operators**, and convert them to a single value with **Value**.



```typescript

// sync iterator

SyncSource = 

  Generators(ex: from, fromConcat, ..etc) | 

  SyncSource.to(To(ex: share, async))

  SyncSource.pipe(

    ...SyncOperators(ex: map, filter, ...etc)

  );



value = SyncSource.value(SyncValues(ex: find,some, ...etc));



// async iterator

AsyncSource = 

  AsyncGenerators(ex: fromAsAsync, fromConcatAsAsync, ...etc) |

  SyncSource.to(asyncSeq()) | // iterable to async iterable. |

  AsyncSource.to(To(ex: shareAsync)) |

  AsyncSource.pipe(

    ...AsyncOperators(ex: mapAsync, filterAsync, ...etc)

  );



value = await AsyncSource.valueAsync(AsyncValues(ex: findAsync,someAsync, ...etc));

```



Because it is a lazy list, it does not execute processing when **pipe()**/**to()** is called, but only when **value(valueAsync)**, **toArray(toArrayAsync)/toMutableArray(toMutableArrayAsync)**, or **forEach(forEachAsync)** is called.



> Changes from "Iterable" or Seq to "Async Iterable" can be made at any time with **.to(asyncSeq())**.

but **Once the chain is changed to "Async Iterable" by **.to(asyncSeq())** or other means, only the asynchronous version of Operator/Value can be used in the same chain thereafter.** This is because, in principle, it is impossible to change from an "Async Iterable" to "Iterable".



The predefined **Generators/Operators/To/Values** are as follows. And all of them have asynchronous versions(*xxxAsAsync* or *xxxAsync*).



If the function you want to use does not exist, you can also define your own Operator/Value function [in this way](https://ugaya40.github.io/leseq/create/).



## Predefined Generators

| Generator | Description |

| --- | --- |

| [defer](https://ugaya40.github.io/leseq/api/generators/#defer) | Generates a sequence that delays the generation of sources until the actual enumeration is performed. (async version: [deferAsAsync](https://ugaya40.github.io/leseq/api/generators/#deferasasync) )  | |

| [deferFromPromise](https://ugaya40.github.io/leseq/api/generators/#deferfrompromise) | **[Async Only]** Generates a sequence whose values are the result of sequential execution of a single Promise or multiple Promises; Promise execution is delayed until the sequence is enumerated.   | |

| [deferValue](https://ugaya40.github.io/leseq/api/generators/#defervalue) | Generates a sequence that delays the generation of the source until the actual enumeration is performed. the source in deferValue consists of a single value. (async version: [deferValueAsAsync](https://ugaya40.github.io/leseq/api/generators/#defervalueasasync) )  | |

| [from](https://ugaya40.github.io/leseq/api/generators/#from) | Generates a sequence from an iterable object. (async version: [fromAsAsync](https://ugaya40.github.io/leseq/api/generators/#fromasasync) ) | |

| [fromConcat](https://ugaya40.github.io/leseq/api/generators/#fromconcat) | Generates a concatenated sequence of multiple iterable objects. (async version: [fromConcatAsAsync](https://ugaya40.github.io/leseq/api/generators/#fromconcatasasync) )  | |

| [fromValue](https://ugaya40.github.io/leseq/api/generators/#fromvalue) | Generates a sequence from a single value. (async version: [fromValueAsAsync](https://ugaya40.github.io/leseq/api/generators/#fromvalueasasync) )  | |

| [range](https://ugaya40.github.io/leseq/api/generators/#range) | Generates a sequential number sequence. (async version: [rangeAsAsync](https://ugaya40.github.io/leseq/api/generators/#rangeasasync) )  | |

| [zip](https://ugaya40.github.io/leseq/api/generators/#zip) | Generates a sequence of arrays made by concatenating the elements of multiple sequences one at a time. (async version: [zipAsAsync](https://ugaya40.github.io/leseq/api/generators/#zipasasync) )  | |



## Predefined To

| To | Description |

| --- | --- |

| [async](https://ugaya40.github.io/leseq/api/to/#async) | Converts the current sequence to AsyncSeq and returns it. | |

| [share](https://ugaya40.github.io/leseq/api/to/#share) | Converts the current sequence to SharedSeq and returns it; in a SharedSeq, `iterator` is share until `close` method is called. (async version: [shareAsync](https://ugaya40.github.io/leseq/api/to/#shareasyncseq) ) | |



## Predefined Operators

It is used within the pipe method of the Seq<T> object. Any number of operators can be connected.



| Operator | Description |

| --- | --- |

| [catchError](https://ugaya40.github.io/leseq/api/operators/#catchError) | If the original iterable sequence raises an exception, the specified action is performed, terminating the enumeration or enumerating an alternate sequence. (async version: [catchErrorAsync](https://ugaya40.github.io/leseq/api/operators/#catcherrorasync) ) | |

| [chunk](https://ugaya40.github.io/leseq/api/operators/#chunk) | Returns a sequence divided into array of the specified size. (async version: [chunkAsync](https://ugaya40.github.io/leseq/api/operators/#chunkasync) )  | |

| [chunkByAccumulation](https://ugaya40.github.io/leseq/api/operators/#chunkbyaccumulation) | Returns a sequence divided into arrays based on an accumulation function and a threshold condition. (async version: [chunkByAccumulationAsync](https://ugaya40.github.io/leseq/api/operators/#chunkbyaccumulationasync) )  | |

| [concat](https://ugaya40.github.io/leseq/api/operators/#concat) | Returns a sequence in which the current sequence and the specified sequence are concatenated. (async version: [concatAsync](https://ugaya40.github.io/leseq/api/operators/#concatasync) )  | |

| [concatValue](https://ugaya40.github.io/leseq/api/operators/#concatvalue) | Returns the sequence to which the specified value is added. (async version: [concatValueAsync](https://ugaya40.github.io/leseq/api/operators/#concatvalueasync) )  | |

| [difference](https://ugaya40.github.io/leseq/api/operators/#difference) | Returns the sequence that is the difference set between the current sequence and the specified sequence. (async version: [differenceAsync](https://ugaya40.github.io/leseq/api/operators/#differenceasync) )  | |

| [filter](https://ugaya40.github.io/leseq/api/operators/#filter) | Returns a sequence that has been filtered by the specified condition. (async version: [filterAsync](https://ugaya40.github.io/leseq/api/operators/#filterasync) )  | |

| [finalize](https://ugaya40.github.io/leseq/api/operators/#finalize) | Invokes a specified action after the source iterable sequence terminates normally or exceptionally. (async version: [finalizeAsync](https://ugaya40.github.io/leseq/api/operators/#finalizeasync) )  | |

| [flatten](https://ugaya40.github.io/leseq/api/operators/#flatten) | Returns a flattened sequence. (async version: [flattenAsync](https://ugaya40.github.io/leseq/api/operators/#flattenasync) )  | |

| [groupBy](https://ugaya40.github.io/leseq/api/operators/#groupby) | Returns a sequence grouped by a specified key. (async version: [groupByAsync](https://ugaya40.github.io/leseq/api/operators/#groupbyasync) )  | |

| [intersect](https://ugaya40.github.io/leseq/api/operators/#intersect) | Returns a sequence that is the product set of the current sequence and the specified sequence. (async version: [intersectAsync](https://ugaya40.github.io/leseq/api/operators/#intersectasync) )  | |

| [map](https://ugaya40.github.io/leseq/api/operators/#map) | Returns the sequence in which each element has been transformed by the specified transformation function. (async version: [mapAsync](https://ugaya40.github.io/leseq/api/operators/#mapasync) )  | |

| [orderBy](https://ugaya40.github.io/leseq/api/operators/#orderby) | Returns a sequence sorted by a specified key. (async version: [orderByAsync](https://ugaya40.github.io/leseq/api/operators/#orderbyasync) )  | |

| [repeat](https://ugaya40.github.io/leseq/api/operators/#repeat) | Returns a sequence that repeats the source sequence a specified number of times. (async version: [repeatAsync](https://ugaya40.github.io/leseq/api/operators/#repeatasync) )  | |

| [reverse](https://ugaya40.github.io/leseq/api/operators/#reverse) | Returns a sequence in reverse order of the current sequence. (async version: [reverseAsync](https://ugaya40.github.io/leseq/api/operators/#reverseasync) )  | |

| [scan](https://ugaya40.github.io/leseq/api/operators/#scan) | Returns the resulting sequence after applying the aggregate function to the elements of the current sequence. (async version: [scanAsync](https://ugaya40.github.io/leseq/api/operators/#scanasync) )  | |

| [skip](https://ugaya40.github.io/leseq/api/operators/#skip) | Returns the sequence with the specified number of skips. (async version: [skipAsync](https://ugaya40.github.io/leseq/api/operators/#skipasync) )  | |

| [skipWhile](https://ugaya40.github.io/leseq/api/operators/#skipwhile) | Returns the sequence of elements skipped while matching the condition. (async version: [skipWhileAsync](https://ugaya40.github.io/leseq/api/operators/#skipwhileasync) )  | |

| [take](https://ugaya40.github.io/leseq/api/operators/#take) | Returns a sequence that enumerates the specified number of items. (async version: [takeAsync](https://ugaya40.github.io/leseq/api/operators/#takeasync) )  | |

| [takeWhile](https://ugaya40.github.io/leseq/api/operators/#takewhile) | Returns a sequence to be enumerated only while the condition is matched. (async version: [takeWhileAsync](https://ugaya40.github.io/leseq/api/operators/#takewhileasync) )  | |

| [tap](https://ugaya40.github.io/leseq/api/operators/#tap) | Run side effects. (async version: [tapAsync](https://ugaya40.github.io/leseq/api/operators/#tapasync) )  | |

| [union](https://ugaya40.github.io/leseq/api/operators/#union) | Returns a sequence that is the union set of the current sequence and the specified sequence. (async version: [unionAsync](https://ugaya40.github.io/leseq/api/operators/#unionasync) )  | |

| [uniq](https://ugaya40.github.io/leseq/api/operators/#uniq) | Returns a deduplicated sequence. (async version: [uniqAsync](https://ugaya40.github.io/leseq/api/operators/#uniqasync) )  | |

| [zipWith](https://ugaya40.github.io/leseq/api/operators/#zipwith) | Returns a sequence of arrays consisting of the elements of the source array and the elements of the multiple sequences given as arguments, concatenated one by one. (async version: [zipWithAsync](https://ugaya40.github.io/leseq/api/operators/#zipwithasync) )  | |



## Predefined Values

Generates a value from a sequence. Used in the value method of the Seq<T> object.



| Value | Description |

| --- | --- |

| [every](https://ugaya40.github.io/leseq/api/values/#every) | Returns whether or not all elements of a sequence meet the specified conditions. (async version: [everyAsync](https://ugaya40.github.io/leseq/api/values/#everyasync) )  | |

| [find](https://ugaya40.github.io/leseq/api/values/#find) | Returns the first element that satisfies the condition. If no element satisfying the condition is found, an error is thrown. (async version: [findAsync](https://ugaya40.github.io/leseq/api/values/#findasync) )  | |

| [findOrDefault](https://ugaya40.github.io/leseq/api/values/#findordefault) | Returns the first element that satisfies the condition. If no element is found that satisfies the condition, it returns the specified default value. (async version: [findOrDefaultAsync](https://ugaya40.github.io/leseq/api/values/#findordefaultasync) )  | |

| [reduce](https://ugaya40.github.io/leseq/api/values/#reduce) | Returns the result of applying the aggregate function to the elements of the current sequence. (async version: [reduceAsync](https://ugaya40.github.io/leseq/api/values/#reduceasync) )  | |

| [some](https://ugaya40.github.io/leseq/api/values/#some) | Returns whether or not any element of the sequence satisfies the specified condition. (async version: [someAsync](https://ugaya40.github.io/leseq/api/values/#someasync) )  | |