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https://github.com/stdlib-js/iter-flow

Create a fluent interface for chaining together iterator methods.
https://github.com/stdlib-js/iter-flow

chain flow fluent funseq iter iterate iterator javascript node node-js nodejs pipe pipeline stdlib stream util utilities utility utils

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Create a fluent interface for chaining together iterator methods.

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README 

        



  

    About stdlib...

  

  
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# iterFlow



[![NPM version][npm-image]][npm-url] [![Build Status][test-image]][test-url] [![Coverage Status][coverage-image]][coverage-url] 



> Create a fluent interface for chaining together [iterator][mdn-iterator-protocol] methods.



## Installation



```bash

npm install @stdlib/iter-flow

```



Alternatively,



-   To load the package in a website via a `script` tag without installation and bundlers, use the [ES Module][es-module] available on the [`esm`][esm-url] branch (see [README][esm-readme]).

-   If you are using Deno, visit the [`deno`][deno-url] branch (see [README][deno-readme] for usage intructions).

-   For use in Observable, or in browser/node environments, use the [Universal Module Definition (UMD)][umd] build available on the [`umd`][umd-url] branch (see [README][umd-readme]).



The [branches.md][branches-url] file summarizes the available branches and displays a diagram illustrating their relationships.



To view installation and usage instructions specific to each branch build, be sure to explicitly navigate to the respective README files on each branch, as linked to above.



## Usage



```javascript

var iterFlow = require( '@stdlib/iter-flow' );

```



#### iterFlow( methods )



Returns a fluent interface [iterator][mdn-iterator-protocol] constructor with a customized `prototype` based on provided `methods`.



```javascript

var iterHead = require( '@stdlib/iter-head' );

var iterSome = require( '@stdlib/iter-some' );



// Create a mini-fluent interface having just the methods `head` and `some`:

var FluentIterator = iterFlow({

    'head': iterHead,

    'some': iterSome

});

```



The `methods` argument should be an `object` which maps constructor method names to [iterator][mdn-iterator-protocol] functions. Each [iterator][mdn-iterator-protocol] function should have the following function signature:



```text

function iterFcn( iterator[, ...args] ) {...}

```



where



-   **iterator**: an [iterator][mdn-iterator-protocol]

-   **...args**: additional [iterator][mdn-iterator-protocol] function arguments



When a fluent interface [iterator][mdn-iterator-protocol] method is invoked, the method invokes the corresponding [iterator][mdn-iterator-protocol] function with an [iterator][mdn-iterator-protocol] and provided method arguments.



If an [iterator][mdn-iterator-protocol] function returns an [iterator][mdn-iterator-protocol], the corresponding fluent interface method returns a **new** fluent interface instance; otherwise, the corresponding fluent interface method returns the [iterator][mdn-iterator-protocol] function result.



* * *



##### FluentIterator( iterator )



Returns a new fluent interface [iterator][mdn-iterator-protocol] from a source [`iterator`][mdn-iterator-protocol].



```javascript

var array2iterator = require( '@stdlib/array-to-iterator' );

var iterHead = require( '@stdlib/iter-head' );

var iterSome = require( '@stdlib/iter-some' );



// Create a mini-fluent interface having just the methods `head` and `some`:

var FluentIterator = iterFlow({

    'head': iterHead,

    'some': iterSome

});



// Create a source iterator:

var src = array2iterator( [ 0, 0, 1, 1, 1, 0, 0, 1, 0, 1 ] );



// Convert the source iterator to a fluent interface iterator:

var it = new FluentIterator( src );



// Test if at least 3 of the first 5 iterated values are truthy:

var bool = it.head( 5 ).some( 3 );

// returns true

```



##### FluentIterator.prototype.next()



Returns an [iterator][mdn-iterator-protocol] protocol-compliant object containing the next iterated value (if one exists) assigned to a `value` property and a `done` property having a `boolean` value indicating whether the [iterator][mdn-iterator-protocol] is finished.



```javascript

var array2iterator = require( '@stdlib/array-to-iterator' );

var iterHead = require( '@stdlib/iter-head' );

var iterSome = require( '@stdlib/iter-some' );



// Create a mini-fluent interface having just the methods `head` and `some`:

var FluentIterator = iterFlow({

    'head': iterHead,

    'some': iterSome

});



// Create a source iterator:

var src = array2iterator( [ 0, 0, 1, 1, 1, 0, 0, 1, 0, 1 ] );



// Create a fluent interface iterator:

var it1 = new FluentIterator( src );



// Invoke the `head` method to return an iterator limited to the first 5 source values:

var it2 = it1.head( 5 );



// Perform manual iteration...

var v;

while ( true ) {

    v = it2.next();

    if ( v.done ) {

        break;

    }

    console.log( v.value );

}

```



##### FluentIterator.prototype.return( \[value] )



Closes a fluent interface [iterator][mdn-iterator-protocol] and returns a single (optional) argument in an [iterator][mdn-iterator-protocol] protocol-compliant object.



```javascript

var array2iterator = require( '@stdlib/array-to-iterator' );

var iterHead = require( '@stdlib/iter-head' );

var iterSome = require( '@stdlib/iter-some' );



// Create a mini-fluent interface having just the methods `head` and `some`:

var FluentIterator = iterFlow({

    'head': iterHead,

    'some': iterSome

});



// Create a source iterator:

var src = array2iterator( [ 0, 0, 1, 1, 1, 0, 0, 1, 0, 1 ] );



// Create a fluent interface iterator:

var it1 = new FluentIterator( src );



// Invoke the `head` method to return an iterator limited to the first 5 source values:

var it2 = it1.head( 5 );



// Get the first value:

var v = it2.next().value;

// returns 0



// Get the second value:

v = it2.next().value;

// returns 0



// Get the third value:

v = it2.next().value;

// returns 1



// Close the iterator:

var bool = it2.return().done;

// returns true



// Attempt to get the fourth value:

v = it2.next().value;

// returns undefined

```



* * *



## Notes



-   The [iterator][mdn-iterator-protocol] function evaluation context is **always** `null`.

-   [Iterator][mdn-iterator-protocol] functions which return [iterators][mdn-iterator-protocol] are **expected** to return [iterator][mdn-iterator-protocol] protocol-compliant objects (i.e., an `object` having a `next` method which returns the next iterated value (if one exists) assigned to a `value` property and a `done` property having a `boolean` value indicating whether the [iterator][mdn-iterator-protocol] is finished).

-   If an environment supports `Symbol.iterator`, the returned iterator is iterable.



* * *



## Examples



```javascript

var array2iterator = require( '@stdlib/array-to-iterator' );

var iterHead = require( '@stdlib/iter-head' );

var iterSome = require( '@stdlib/iter-some' );

var iterFlow = require( '@stdlib/iter-flow' );



// Create a "fluent" interface:

var FluentIterator = iterFlow({

    'head': iterHead,

    'some': iterSome

});



// Create a source iterator:

var arr = array2iterator( [ 0, 0, 1, 1, 1, 0, 0, 1, 0, 1 ] );



// Create a new iterator:

var it = new FluentIterator( arr );



var bool = it.head( 5 ).some( 3 );

// returns true



// Create another source iterator:

arr = array2iterator( [ 0, 0, 1, 0, 1, 0, 0, 1, 0, 1 ] );



// Create a new iterator:

it = new FluentIterator( arr );



bool = it.head( 5 ).some( 3 );

// returns false

```



* * *



## See Also



-   [`@stdlib/iter-pipeline`][@stdlib/iter/pipeline]: create an iterator pipeline.



* * *



## Notice



This package is part of [stdlib][stdlib], a standard library for JavaScript and Node.js, with an emphasis on numerical and scientific computing. The library provides a collection of robust, high performance libraries for mathematics, statistics, streams, utilities, and more.



For more information on the project, filing bug reports and feature requests, and guidance on how to develop [stdlib][stdlib], see the main project [repository][stdlib].



#### Community



[![Chat][chat-image]][chat-url]



---



## License



See [LICENSE][stdlib-license].



## Copyright



Copyright © 2016-2024. The Stdlib [Authors][stdlib-authors].



[npm-image]: http://img.shields.io/npm/v/@stdlib/iter-flow.svg

[npm-url]: https://npmjs.org/package/@stdlib/iter-flow



[test-image]: https://github.com/stdlib-js/iter-flow/actions/workflows/test.yml/badge.svg?branch=main

[test-url]: https://github.com/stdlib-js/iter-flow/actions/workflows/test.yml?query=branch:main



[coverage-image]: https://img.shields.io/codecov/c/github/stdlib-js/iter-flow/main.svg

[coverage-url]: https://codecov.io/github/stdlib-js/iter-flow?branch=main



[chat-image]: https://img.shields.io/gitter/room/stdlib-js/stdlib.svg

[chat-url]: https://app.gitter.im/#/room/#stdlib-js_stdlib:gitter.im



[stdlib]: https://github.com/stdlib-js/stdlib



[stdlib-authors]: https://github.com/stdlib-js/stdlib/graphs/contributors



[umd]: https://github.com/umdjs/umd

[es-module]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Modules



[deno-url]: https://github.com/stdlib-js/iter-flow/tree/deno

[deno-readme]: https://github.com/stdlib-js/iter-flow/blob/deno/README.md

[umd-url]: https://github.com/stdlib-js/iter-flow/tree/umd

[umd-readme]: https://github.com/stdlib-js/iter-flow/blob/umd/README.md

[esm-url]: https://github.com/stdlib-js/iter-flow/tree/esm

[esm-readme]: https://github.com/stdlib-js/iter-flow/blob/esm/README.md

[branches-url]: https://github.com/stdlib-js/iter-flow/blob/main/branches.md



[stdlib-license]: https://raw.githubusercontent.com/stdlib-js/iter-flow/main/LICENSE



[mdn-iterator-protocol]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Iteration_protocols#The_iterator_protocol



[@stdlib/iter/pipeline]: https://github.com/stdlib-js/iter-pipeline