{"id":20489303,"url":"https://github.com/stdlib-js/iter-unique-by-hash","last_synced_at":"2026-02-26T19:43:02.716Z","repository":{"id":41358826,"uuid":"376897980","full_name":"stdlib-js/iter-unique-by-hash","owner":"stdlib-js","description":"Create an iterator which returns unique values according to a hash function.","archived":false,"fork":false,"pushed_at":"2025-04-07T01:13:01.000Z","size":1017,"stargazers_count":2,"open_issues_count":0,"forks_count":0,"subscribers_count":3,"default_branch":"main","last_synced_at":"2025-05-21T15:23:57.553Z","etag":null,"topics":["dedupe","deduplicate","distinct","hash","iterable","iterate","iterator","javascript","node","node-js","nodejs","stdlib","uniq","unique","util","utilities","utility","utils"],"latest_commit_sha":null,"homepage":"https://github.com/stdlib-js/stdlib","language":"JavaScript","has_issues":false,"has_wiki":null,"has_pages":null,"mirror_url":null,"source_name":null,"license":"apache-2.0","status":null,"scm":"git","pull_requests_enabled":true,"icon_url":"https://github.com/stdlib-js.png","metadata":{"files":{"readme":"README.md","changelog":"CHANGELOG.md","contributing":"CONTRIBUTING.md","funding":null,"license":"LICENSE","code_of_conduct":"CODE_OF_CONDUCT.md","threat_model":null,"audit":null,"citation":"CITATION.cff","codeowners":null,"security":"SECURITY.md","support":null,"governance":null,"roadmap":null,"authors":null,"dei":null,"publiccode":null,"codemeta":null,"zenodo":null},"funding":{"github":["stdlib-js"],"open_collective":"stdlib","tidelift":"npm/@stdlib/stdlib"}},"created_at":"2021-06-14T17:03:05.000Z","updated_at":"2025-04-07T00:54:36.000Z","dependencies_parsed_at":"2023-02-17T06:31:14.560Z","dependency_job_id":"809d69e9-e9de-4159-b7d4-80e40f152097","html_url":"https://github.com/stdlib-js/iter-unique-by-hash","commit_stats":{"total_commits":49,"total_committers":1,"mean_commits":49.0,"dds":0.0,"last_synced_commit":"fe366f277aa3e0eb0da66ebb41c5ba34d4904d66"},"previous_names":[],"tags_count":27,"template":false,"template_full_name":null,"purl":"pkg:github/stdlib-js/iter-unique-by-hash","repository_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub/repositories/stdlib-js%2Fiter-unique-by-hash","tags_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub/repositories/stdlib-js%2Fiter-unique-by-hash/tags","releases_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub/repositories/stdlib-js%2Fiter-unique-by-hash/releases","manifests_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub/repositories/stdlib-js%2Fiter-unique-by-hash/manifests","owner_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub/owners/stdlib-js","download_url":"https://codeload.github.com/stdlib-js/iter-unique-by-hash/tar.gz/refs/heads/main","sbom_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub/repositories/stdlib-js%2Fiter-unique-by-hash/sbom","host":{"name":"GitHub","url":"https://github.com","kind":"github","repositories_count":261676328,"owners_count":23192766,"icon_url":"https://github.com/github.png","version":null,"created_at":"2022-05-30T11:31:42.601Z","updated_at":"2022-07-04T15:15:14.044Z","host_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub","repositories_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub/repositories","repository_names_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub/repository_names","owners_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub/owners"}},"keywords":["dedupe","deduplicate","distinct","hash","iterable","iterate","iterator","javascript","node","node-js","nodejs","stdlib","uniq","unique","util","utilities","utility","utils"],"created_at":"2024-11-15T17:12:17.249Z","updated_at":"2026-02-26T19:43:02.710Z","avatar_url":"https://github.com/stdlib-js.png","language":"JavaScript","funding_links":["https://github.com/sponsors/stdlib-js","https://opencollective.com/stdlib","https://tidelift.com/funding/github/npm/@stdlib/stdlib"],"categories":[],"sub_categories":[],"readme":"\u003c!--\n\n@license Apache-2.0\n\nCopyright (c) 2019 The Stdlib Authors.\n\nLicensed under the Apache License, Version 2.0 (the \"License\");\nyou may not use this file except in compliance with the License.\nYou may obtain a copy of the License at\n\n   http://www.apache.org/licenses/LICENSE-2.0\n\nUnless required by applicable law or agreed to in writing, software\ndistributed under the License is distributed on an \"AS IS\" BASIS,\nWITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.\nSee the License for the specific language governing permissions and\nlimitations under the License.\n\n--\u003e\n\n\n\u003cdetails\u003e\n  \u003csummary\u003e\n    About stdlib...\n  \u003c/summary\u003e\n  \u003cp\u003eWe 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.\u003c/p\u003e\n  \u003cp\u003eThe 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.\u003c/p\u003e\n  \u003cp\u003eWhen 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.\u003c/p\u003e\n  \u003cp\u003eTo join us in bringing numerical computing to the web, get started by checking us out on \u003ca href=\"https://github.com/stdlib-js/stdlib\"\u003eGitHub\u003c/a\u003e, and please consider \u003ca href=\"https://opencollective.com/stdlib\"\u003efinancially supporting stdlib\u003c/a\u003e. We greatly appreciate your continued support!\u003c/p\u003e\n\u003c/details\u003e\n\n# iterUniqueByHash\n\n[![NPM version][npm-image]][npm-url] [![Build Status][test-image]][test-url] [![Coverage Status][coverage-image]][coverage-url] \u003c!-- [![dependencies][dependencies-image]][dependencies-url] --\u003e\n\n\u003e Create an [iterator][mdn-iterator-protocol] which returns unique values according to a hash function.\n\n\u003c!-- Section to include introductory text. Make sure to keep an empty line after the intro `section` element and another before the `/section` close. --\u003e\n\n\u003csection class=\"intro\"\u003e\n\n\u003c/section\u003e\n\n\u003c!-- /.intro --\u003e\n\n\u003c!-- Package usage documentation. --\u003e\n\n\u003csection class=\"installation\"\u003e\n\n## Installation\n\n```bash\nnpm install @stdlib/iter-unique-by-hash\n```\n\nAlternatively,\n\n-   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]).\n-   If you are using Deno, visit the [`deno`][deno-url] branch (see [README][deno-readme] for usage intructions).\n-   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]).\n\nThe [branches.md][branches-url] file summarizes the available branches and displays a diagram illustrating their relationships.\n\nTo 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.\n\n\u003c/section\u003e\n\n\u003csection class=\"usage\"\u003e\n\n## Usage\n\n```javascript\nvar iterUniqueByHash = require( '@stdlib/iter-unique-by-hash' );\n```\n\n#### iterUniqueByHash( iterator, hashFcn\\[, thisArg] )\n\nReturns an [iterator][mdn-iterator-protocol] which returns unique values according to a hash function.\n\n```javascript\nvar array2iterator = require( '@stdlib/array-to-iterator' );\n\nfunction hashFcn( v ) {\n    return v;\n}\n\nvar src = array2iterator( [ 2, 1, 1, 2, 4, 3, 4, 3 ] );\n\nvar it = iterUniqueByHash( src, hashFcn );\n// returns \u003cObject\u003e\n\nvar v = it.next().value;\n// returns 2\n\nv = it.next().value;\n// returns 1\n\nv = it.next().value;\n// returns 4\n\nv = it.next().value;\n// returns 3\n\nvar bool = it.next().done;\n// returns true\n```\n\nThe returned [iterator][mdn-iterator-protocol] protocol-compliant object has the following properties:\n\n-   **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][mdn-iterator-protocol] is finished.\n-   **return**: function which closes an [iterator][mdn-iterator-protocol] and returns a single (optional) argument in an [iterator][mdn-iterator-protocol] protocol-compliant object.\n\nA hash function is provided one argument:\n\n-   **v**: the current iterated value.\n\nTo set the execution context of the hash function, provide a `thisArg`.\n\n\u003c!-- eslint-disable object-curly-newline --\u003e\n\n```javascript\nvar array2iterator = require( '@stdlib/array-to-iterator' );\n\nfunction hashFcn( v ) {\n    this.count += 1;\n    return JSON.stringify( v );\n}\n\nvar values = [\n    { 'v': 2 },\n    { 'v': 1 },\n    { 'v': 1 },\n    { 'v': 2 },\n    { 'v': 4 },\n    { 'v': 3 },\n    { 'v': 4 },\n    { 'v': 3 }\n];\n\nvar src = array2iterator( values );\n\nvar ctx = {\n    'count': 0\n};\n\nvar it = iterUniqueByHash( src, hashFcn, ctx );\n// returns \u003cObject\u003e\n\nvar v = it.next().value;\n// returns { 'v': 2 }\n\nv = it.next().value;\n// returns { 'v': 1 }\n\nv = it.next().value;\n// returns { 'v': 4 }\n\nv = it.next().value;\n// returns { 'v': 3 }\n\nvar bool = it.next().done;\n// returns true\n\nbool = ( ctx.count \u003e 0 );\n// returns true\n```\n\n\u003c/section\u003e\n\n\u003c!-- /.usage --\u003e\n\n\u003c!-- Package usage notes. Make sure to keep an empty line after the `section` element and another before the `/section` close. --\u003e\n\n\u003csection class=\"notes\"\u003e\n\n## Notes\n\n-   A returned [iterator][mdn-iterator-protocol] internally buffers unique hashes and, thus, has `O(N)` memory requirements.\n-   An iterated value is considered \"unique\" if a hash function returns a unique hash value for that iterated value. Beware that this _may_ result in unexpected behavior. Namely, only the **first** iterated value mapping to a particular hash function result is returned, even if subsequent values, while mapping to the same hash, are different. Accordingly, iteration order **does** matter.\n-   If an environment supports `Symbol.iterator` **and** a provided [iterator][mdn-iterator-protocol] is iterable, the returned [iterator][mdn-iterator-protocol] is iterable.\n\n\u003c/section\u003e\n\n\u003c!-- /.notes --\u003e\n\n\u003c!-- Package usage examples. --\u003e\n\n\u003csection class=\"examples\"\u003e\n\n## Examples\n\n\u003c!-- eslint no-undef: \"error\" --\u003e\n\n```javascript\nvar discreteUniform = require( '@stdlib/random-iter-discrete-uniform' );\nvar iterMap = require( '@stdlib/iter-map' );\nvar iterUniqueByHash = require( '@stdlib/iter-unique-by-hash' );\n\nfunction mapFcn( v ) {\n    return {\n        'v': v\n    };\n}\n\nfunction hashFcn( v ) {\n    return JSON.stringify( v );\n}\n\n// Create a seeded iterator which can generate 1000 pseudorandom numbers:\nvar rand = discreteUniform( 1, 10, {\n    'seed': 1234,\n    'iter': 1000\n});\n\n// Create an iterator which maps each number to an object:\nvar miter = iterMap( rand, mapFcn );\n\n// Create an iterator which returns unique (object) values:\nvar it = iterUniqueByHash( miter, hashFcn );\n\n// Perform manual iteration...\nvar v;\nwhile ( true ) {\n    v = it.next();\n    if ( v.done ) {\n        break;\n    }\n    console.log( v.value );\n}\n```\n\n\u003c/section\u003e\n\n\u003c!-- /.examples --\u003e\n\n\u003c!-- 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. --\u003e\n\n\u003csection class=\"references\"\u003e\n\n\u003c/section\u003e\n\n\u003c!-- /.references --\u003e\n\n\u003c!-- Section for related `stdlib` packages. Do not manually edit this section, as it is automatically populated. --\u003e\n\n\u003csection class=\"related\"\u003e\n\n* * *\n\n## See Also\n\n-   \u003cspan class=\"package-name\"\u003e[`@stdlib/iter-unique`][@stdlib/iter/unique]\u003c/span\u003e\u003cspan class=\"delimiter\"\u003e: \u003c/span\u003e\u003cspan class=\"description\"\u003ecreate an iterator which returns unique values.\u003c/span\u003e\n-   \u003cspan class=\"package-name\"\u003e[`@stdlib/iter-unique-by`][@stdlib/iter/unique-by]\u003c/span\u003e\u003cspan class=\"delimiter\"\u003e: \u003c/span\u003e\u003cspan class=\"description\"\u003ecreate an iterator which returns unique values according to a predicate function.\u003c/span\u003e\n\n\u003c/section\u003e\n\n\u003c!-- /.related --\u003e\n\n\u003c!-- Section for all links. Make sure to keep an empty line after the `section` element and another before the `/section` close. --\u003e\n\n\n\u003csection class=\"main-repo\" \u003e\n\n* * *\n\n## Notice\n\nThis 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.\n\nFor 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].\n\n#### Community\n\n[![Chat][chat-image]][chat-url]\n\n---\n\n## License\n\nSee [LICENSE][stdlib-license].\n\n\n## Copyright\n\nCopyright \u0026copy; 2016-2026. The Stdlib [Authors][stdlib-authors].\n\n\u003c/section\u003e\n\n\u003c!-- /.stdlib --\u003e\n\n\u003c!-- Section for all links. Make sure to keep an empty line after the `section` element and another before the `/section` close. --\u003e\n\n\u003csection class=\"links\"\u003e\n\n[npm-image]: http://img.shields.io/npm/v/@stdlib/iter-unique-by-hash.svg\n[npm-url]: https://npmjs.org/package/@stdlib/iter-unique-by-hash\n\n[test-image]: https://github.com/stdlib-js/iter-unique-by-hash/actions/workflows/test.yml/badge.svg?branch=v0.2.3\n[test-url]: https://github.com/stdlib-js/iter-unique-by-hash/actions/workflows/test.yml?query=branch:v0.2.3\n\n[coverage-image]: https://img.shields.io/codecov/c/github/stdlib-js/iter-unique-by-hash/main.svg\n[coverage-url]: https://codecov.io/github/stdlib-js/iter-unique-by-hash?branch=main\n\n\u003c!--\n\n[dependencies-image]: https://img.shields.io/david/stdlib-js/iter-unique-by-hash.svg\n[dependencies-url]: https://david-dm.org/stdlib-js/iter-unique-by-hash/main\n\n--\u003e\n\n[chat-image]: https://img.shields.io/badge/zulip-join_chat-brightgreen.svg\n[chat-url]: https://stdlib.zulipchat.com\n\n[stdlib]: https://github.com/stdlib-js/stdlib\n\n[stdlib-authors]: https://github.com/stdlib-js/stdlib/graphs/contributors\n\n[umd]: https://github.com/umdjs/umd\n[es-module]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Modules\n\n[deno-url]: https://github.com/stdlib-js/iter-unique-by-hash/tree/deno\n[deno-readme]: https://github.com/stdlib-js/iter-unique-by-hash/blob/deno/README.md\n[umd-url]: https://github.com/stdlib-js/iter-unique-by-hash/tree/umd\n[umd-readme]: https://github.com/stdlib-js/iter-unique-by-hash/blob/umd/README.md\n[esm-url]: https://github.com/stdlib-js/iter-unique-by-hash/tree/esm\n[esm-readme]: https://github.com/stdlib-js/iter-unique-by-hash/blob/esm/README.md\n[branches-url]: https://github.com/stdlib-js/iter-unique-by-hash/blob/main/branches.md\n\n[stdlib-license]: https://raw.githubusercontent.com/stdlib-js/iter-unique-by-hash/main/LICENSE\n\n[mdn-iterator-protocol]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Iteration_protocols#The_iterator_protocol\n\n\u003c!-- \u003crelated-links\u003e --\u003e\n\n[@stdlib/iter/unique]: https://github.com/stdlib-js/iter-unique\n\n[@stdlib/iter/unique-by]: https://github.com/stdlib-js/iter-unique-by\n\n\u003c!-- \u003c/related-links\u003e --\u003e\n\n\u003c/section\u003e\n\n\u003c!-- /.links --\u003e\n","project_url":"https://awesome.ecosyste.ms/api/v1/projects/github.com%2Fstdlib-js%2Fiter-unique-by-hash","html_url":"https://awesome.ecosyste.ms/projects/github.com%2Fstdlib-js%2Fiter-unique-by-hash","lists_url":"https://awesome.ecosyste.ms/api/v1/projects/github.com%2Fstdlib-js%2Fiter-unique-by-hash/lists"}