@stdlib/utils-inmap

<details> <summary> About stdlib... </summary> <p>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.</p> <p>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.</p> <p>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.</p> <p>To join us in bringing numerical computing to the web, get started by checking us out on <a href="https://github.com/stdlib-js/stdlib">GitHub</a>, and please consider <a href="https://opencollective.com/stdlib">financially supporting stdlib</a>. We greatly appreciate your continued support!</p> </details> # inmap [![NPM version][npm-image]][npm-url] [![Build Status][test-image]][test-url] [![Coverage Status][coverage-image]][coverage-url]  > Invoke a function for each element in a collection and update the collection in-place.  <section class="intro"> </section>   <section class="installation"> ## Installation ```bash npm install @stdlib/utils-inmap ``` </section> <section class="usage"> ## Usage ```javascript var inmap = require( '@stdlib/utils-inmap' ); ``` #### inmap( collection, fcn\[, thisArg ] ) Invokes a `function` for each element in a `collection` and updates the `collection` in-place. ```javascript function scale( value, index ) { return value * index; } var arr = [ 1, 2, 3, 4 ]; var out = inmap( arr, scale ); // returns [ 0, 2, 6, 12 ] var bool = ( out === arr ); // returns true ``` The invoked `function` is provided three arguments: - `value`: collection element - `index`: collection index - `collection`: input collection Basic support for dynamic collections is provided. Note, however, that index incrementation is monotonically increasing. ```javascript function scale1( value, index, collection ) { if ( index === collection.length-1 && collection.length < 10 ) { collection.push( index+2 ); } return value * index; } var arr = [ 1, 2, 3, 4 ]; var out = inmap( arr, scale1 ); // returns [ 0, 2, 6, 12, 20, 30, 42, 56, 72, 90 ] function scale2( value, index, collection ) { collection.shift(); return value * index; } arr = [ 1, 2, 3, 4 ]; out = inmap( arr, scale2 ); // returns [ 3, 3 ] ``` To set the function execution context, provide a `thisArg`. ```javascript function sum( value ) { this.sum += value; this.count += 1; return value; } var arr = [ 1, 2, 3, 4 ]; var context = { 'sum': 0, 'count': 0 }; var out = inmap( arr, sum, context ); // returns [ 1, 2, 3, 4 ] var mean = context.sum / context.count; // returns 2.5 ``` </section>   <section class="notes"> ## Notes - A `collection` may be either an [`Array`][mdn-array], [`Typed Array`][mdn-typed-array], or an array-like [`Object`][mdn-object] (excluding `strings` and `functions`). - The function differs from [`Array.prototype.map`][mdn-array-map] in the following ways: - The function returns the input `collection`. - The function modifies `collection` elements in-place. - The function does **not** skip `undefined` elements.  ```javascript function log( value, index ) { console.log( '%s: %s', index, value ); return value; } var arr = [ 1, , , 4 ]; var out = inmap( arr, log ); /* => 0: 1 1: undefined 2: undefined 3: 4 */ ``` - The function provides limited support for dynamic collections (i.e., collections whose `length` changes during execution). </section>   <section class="examples"> ## Examples  ```javascript var isEven = require( '@stdlib/assert-is-even' ).isPrimitive; var inmap = require( '@stdlib/utils-inmap' ); var bool; var arr; var out; var i; function scale( value, index, collection ) { if ( isEven( index ) ) { collection.shift(); } else { collection.push( index+1 ); } return value * index; } arr = new Array( 100 ); for ( i = 0; i < arr.length; i++ ) { arr[ i ] = i; } out = inmap( arr, scale ); bool = ( out === arr ); console.log( bool ); console.log( out ); ``` </section>   <section class="references"> </section>   <section class="related"> * * * ## See Also - <span class="package-name">[`@stdlib/utils-for-each`][@stdlib/utils/for-each]</span><span class="delimiter">: </span><span class="description">invoke a function for each element in a collection.</span> - <span class="package-name">[`@stdlib/utils-inmap-right`][@stdlib/utils/inmap-right]</span><span class="delimiter">: </span><span class="description">invoke a function for each element in a collection and update the collection in-place, iterating from right to left.</span> - <span class="package-name">[`@stdlib/utils-map`][@stdlib/utils/map]</span><span class="delimiter">: </span><span class="description">apply a function to each element in an array and assign the result to an element in an output array.</span> </section>   <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 © 2016-2024. The Stdlib [Authors][stdlib-authors]. </section>   <section class="links"> [npm-image]: http://img.shields.io/npm/v/@stdlib/utils-inmap.svg [npm-url]: https://npmjs.org/package/@stdlib/utils-inmap [test-image]: https://github.com/stdlib-js/utils-inmap/actions/workflows/test.yml/badge.svg?branch=v0.2.2 [test-url]: https://github.com/stdlib-js/utils-inmap/actions/workflows/test.yml?query=branch:v0.2.2 [coverage-image]: https://img.shields.io/codecov/c/github/stdlib-js/utils-inmap/main.svg [coverage-url]: https://codecov.io/github/stdlib-js/utils-inmap?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/utils-inmap/tree/deno [deno-readme]: https://github.com/stdlib-js/utils-inmap/blob/deno/README.md [umd-url]: https://github.com/stdlib-js/utils-inmap/tree/umd [umd-readme]: https://github.com/stdlib-js/utils-inmap/blob/umd/README.md [esm-url]: https://github.com/stdlib-js/utils-inmap/tree/esm [esm-readme]: https://github.com/stdlib-js/utils-inmap/blob/esm/README.md [branches-url]: https://github.com/stdlib-js/utils-inmap/blob/main/branches.md [stdlib-license]: https://raw.githubusercontent.com/stdlib-js/utils-inmap/main/LICENSE [mdn-array]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array [mdn-typed-array]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray [mdn-object]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object [mdn-array-map]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/map  [@stdlib/utils/for-each]: https://www.npmjs.com/package/@stdlib/utils-for-each [@stdlib/utils/inmap-right]: https://www.npmjs.com/package/@stdlib/utils-inmap-right [@stdlib/utils/map]: https://www.npmjs.com/package/@stdlib/utils-map  </section>