Ecosyste.ms: Awesome

An open API service indexing awesome lists of open source software.

Awesome Lists | Featured Topics | Projects

https://github.com/stdlib-js/iter-do-while-each

Create an iterator which, while a test condition is true, invokes a function for each iterated value before returning the iterated value.
https://github.com/stdlib-js/iter-do-while-each

do-while-each each iterable iterate iterator iterdowhileeach javascript node node-js nodejs stdlib util utilities utility utils while whileeach

Last synced: 21 days ago
JSON representation

Create an iterator which, while a test condition is true, invokes a function for each iterated value before returning the iterated value.

Awesome Lists containing this project

README 

        



  

    About stdlib...

  

  
We believe in a future in which the web is a preferred environment for numerical computation. To help realize this future, we've built stdlib. stdlib is a standard library, with an emphasis on numerical and scientific computation, written in JavaScript (and C) for execution in browsers and in Node.js.


  
The library is fully decomposable, being architected in such a way that you can swap out and mix and match APIs and functionality to cater to your exact preferences and use cases.


  
When you use stdlib, you can be absolutely certain that you are using the most thorough, rigorous, well-written, studied, documented, tested, measured, and high-quality code out there.


  
To join us in bringing numerical computing to the web, get started by checking us out on GitHub, and please consider financially supporting stdlib. We greatly appreciate your continued support!



# iterDoWhileEach



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



> Create an iterator which, while a test condition is true, invokes a function for each iterated value before returning the iterated value.



## Installation



```bash

npm install @stdlib/iter-do-while-each

```



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 iterDoWhileEach = require( '@stdlib/iter-do-while-each' );

```



#### iterDoWhileEach( iterator, predicate, fcn\[, thisArg] )



Returns an iterator which invokes a function for each iterated value before returning the iterated value until either a predicate function returns false or the iterator has iterated over all values. The condition is evaluated after executing the provided function (fcn).



```javascript

var iterDoWhileEach = require( '@stdlib/iter-do-while-each' );

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



function predicate( v ) {

    return v < 3;

}



function assert( v ) {

    if ( v !== v ) {

        throw new Error( 'should not be NaN' );

    }

}



var it = iterDoWhileEach( array2iterator( [ 1, 2, 3, 4 ] ), predicate, assert );

// returns {}



var r = it.next().value;

// returns 1



r = it.next().value;

// returns 2



r = it.next().value;

// returns undefined



// ...

```



The returned iterator protocol-compliant object has the following properties:



-   **next**: function which returns an iterator 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 is finished.

-   **return**: function which closes an iterator and returns a single (optional) argument in an iterator protocol-compliant object.



Both the `predicate` function and the function to invoke for each iterated value are provided two arguments:



-   **value**: iterated value

-   **index**: iteration index (zero-based)



```javascript

var iterDoWhileEach = require( '@stdlib/iter-do-while-each' );

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



function predicate( v ) {

    return v < 3;

}



function assert( v, i ) {

    if ( v !== v ) {

        throw new Error( 'should not be NaN' );

    }

}



var it = iterDoWhileEach( array2iterator( [ 1, 2, 3, 4 ] ), predicate, assert );

// returns 



var r = it.next().value;

// returns 1



r = it.next().value;

// returns 2



r = it.next().value;

// returns undefined

// ...

```



To set the execution context for `fcn`, provide a `thisArg`.



```javascript

var iterDoWhileEach = require( '@stdlib/iter-do-while-each' );

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



function assert( v ) {

    this.count += 1;

    if ( v !== v ) {

        throw new Error( 'should not be NaN' );

    }

}



function predicate( v ) {

    return v < 3;

}



var ctx = {

    'count': 0

};



var iterator = array2iterator( [ 1, 2, 3 ] );

var it = iterDoWhileEach( iterator, predicate, assert, ctx );

// returns 



var r = it.next().value;

// returns 1



r = it.next().value;

// returns 2



r = it.next().value;

// returns undefined



var count = ctx.count;

// returns 3

```



## Notes



-   If an environment supports `Symbol.iterator` **and** a provided iterator is iterable, the returned iterator is iterable.



## Examples



```javascript

var randu = require( '@stdlib/random-iter-randu' );

var isnan = require( '@stdlib/math-base-assert-is-nan' );

var iterDoWhileEach = require( '@stdlib/iter-do-while-each' );



function assert( v ) {

    if ( isnan( v ) ) {

        throw new Error( 'should not be NaN' );

    }

}



function predicate( v ) {

    return v <= 0.75;

}



// Create a seeded iterator for generating pseudorandom numbers:

var rand = randu({

    'seed': 1234,

    'iter': 10

});



// Create an iterator which validates generated numbers:

var it = iterDoWhileEach( rand, predicate, assert );



// Perform manual iteration...

var r;

while ( true ) {

    r = it.next();

    if ( r.done ) {

        break;

    }

    console.log( r.value );

}

```



* * *



## 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-do-while-each.svg

[npm-url]: https://npmjs.org/package/@stdlib/iter-do-while-each



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

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



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

[coverage-url]: https://codecov.io/github/stdlib-js/iter-do-while-each?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-do-while-each/tree/deno

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

[umd-url]: https://github.com/stdlib-js/iter-do-while-each/tree/umd

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

[esm-url]: https://github.com/stdlib-js/iter-do-while-each/tree/esm

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

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



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