npm package: @stdlib/math-iter-tools-map
Description: Create an iterator which invokes a unary function accepting a single numeric argument for each iterated value.
Author: The Stdlib Authors
Latest version: 0.2.3

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<details>
  <summary>
    About stdlib...
  </summary>
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</details>

# iterMap

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

> Create an [iterator][mdn-iterator-protocol] which invokes a unary function accepting a single numeric argument for each iterated value.

<!-- Section to include introductory text. Make sure to keep an empty line after the intro `section` element and another before the `/section` close. -->

<section class="intro">

</section>

<!-- /.intro -->

<!-- Package usage documentation. -->

<section class="installation">

## Installation

```bash
npm install @stdlib/math-iter-tools-map
```

</section>

<section class="usage">

## Usage

```javascript
var iterMap = require( '@stdlib/math-iter-tools-map' );
```

#### iterMap( iterator, fcn\[, options] )

Returns an [iterator][mdn-iterator-protocol] which invokes a unary `function` accepting a single numeric argument for each iterated value.

```javascript
var array2iterator = require( '@stdlib/array-to-iterator' );
var sin = require( '@stdlib/math-base-special-sin' );

var it = iterMap( array2iterator( [ 1, 2, 3, 4 ] ), sin );
// returns <Object>

var r = it.next().value;
// returns <number>

r = it.next().value;
// returns <number>

r = it.next().value;
// returns <number>

// ...
```

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

-   **next**: function which 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 is finished.
-   **return**: function which closes an [iterator][mdn-iterator-protocol] and returns a single (optional) argument in an [iterator][mdn-iterator-protocol] protocol-compliant object.

The invoked `function` is provided one argument:

-   `value`: iterated value.

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

function fcn( v ) {
    return v + 10;
}

var it = iterMap( array2iterator( [ 1, 2, 3, 4 ] ), fcn );
// returns <Object>

var r = it.next().value;
// returns 11

r = it.next().value;
// returns 12

r = it.next().value;
// returns 13

// ...
```

The function supports the following `options`:

-   **invalid**: return value when an input [iterator][mdn-iterator-protocol] yields a non-numeric value. Default: `NaN`.

By default, the function returns an [iterator][mdn-iterator-protocol] which returns `NaN` when an input [iterator][mdn-iterator-protocol] yields a non-numeric value. To specify a different return value, set the `invalid` option.

```javascript
var array2iterator = require( '@stdlib/array-to-iterator' );
var sin = require( '@stdlib/math-base-special-sin' );

var opts = {
    'invalid': null
};
var it = iterMap( array2iterator( [ '1', '2', '3' ] ), sin, opts );
// returns <Object>

var v = it.next().value;
// returns null

v = it.next().value;
// returns null

// ...
```

</section>

<!-- /.usage -->

<!-- Package usage notes. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->

<section class="notes">

## Notes

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

</section>

<!-- /.notes -->

<!-- Package usage examples. -->

<section class="examples">

## Examples

<!-- eslint no-undef: "error" -->

```javascript
var randu = require( '@stdlib/random-iter-randu' );
var sin = require( '@stdlib/math-base-special-sin' );
var iterMap = require( '@stdlib/math-iter-tools-map' );

// Create a seeded iterator for generating pseudorandom numbers:
var rand = randu({
    'seed': 1234,
    'iter': 10
});

// Create an iterator which consumes the pseudorandom number iterator:
var it = iterMap( rand, sin );

// Perform manual iteration...
var r;
while ( true ) {
    r = it.next();
    if ( r.done ) {
        break;
    }
    console.log( r.value );
}
```

</section>

<!-- /.examples -->

<!-- Section to include cited references. If references are included, add a horizontal rule *before* the section. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->

<section class="references">

</section>

<!-- /.references -->

<!-- Section for related `stdlib` packages. Do not manually edit this section, as it is automatically populated. -->

<section class="related">

</section>

<!-- /.related -->

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<section class="main-repo" >

* * *

## 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 &copy; 2016-2026. The Stdlib [Authors][stdlib-authors].

</section>

<!-- /.stdlib -->

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[npm-image]: http://img.shields.io/npm/v/@stdlib/math-iter-tools-map.svg
[npm-url]: https://npmjs.org/package/@stdlib/math-iter-tools-map

[test-image]: https://github.com/stdlib-js/math-iter-tools-map/actions/workflows/test.yml/badge.svg?branch=v0.2.3
[test-url]: https://github.com/stdlib-js/math-iter-tools-map/actions/workflows/test.yml?query=branch:v0.2.3

[coverage-image]: https://img.shields.io/codecov/c/github/stdlib-js/math-iter-tools-map/main.svg
[coverage-url]: https://codecov.io/github/stdlib-js/math-iter-tools-map?branch=main

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[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/math-iter-tools-map/tree/deno
[deno-readme]: https://github.com/stdlib-js/math-iter-tools-map/blob/deno/README.md
[umd-url]: https://github.com/stdlib-js/math-iter-tools-map/tree/umd
[umd-readme]: https://github.com/stdlib-js/math-iter-tools-map/blob/umd/README.md
[esm-url]: https://github.com/stdlib-js/math-iter-tools-map/tree/esm
[esm-readme]: https://github.com/stdlib-js/math-iter-tools-map/blob/esm/README.md
[branches-url]: https://github.com/stdlib-js/math-iter-tools-map/blob/main/branches.md

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

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

</section>

<!-- /.links -->