A lightweight, and docile, JavaScript (ES5) library to help embracing functional programming.





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Lamb, because it's docile like a lamb.

A lightweight, and docile, JavaScript (ES5) library to help embracing functional programming.

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Lamb logo


The API documentation is here.

Installation and basic usage.

Install it with npm:

npm install lamb

Require it in node.js:

const _ = require("lamb");

Since version 0.57.0, Lamb is splitted in ES modules and can take advantage of tree-shaking capabilities of module bundlers:

import * as _ from "lamb";

You can also import only the functions you want to use:

import { compose, map } from "lamb";

In a browser, simply include the version you want from the dist folder:

<script src="dist/lamb.js"></script>


<script src="dist/lamb.min.js"></script>

Doing so a lamb variable will be created in the global object. The source map for the minified file is in the same dist folder.

Since version 0.58.0 there is also a one file ES modules build, always in the dist folder, named lamb.mjs (previously lamb.esm.js) and its minified version lamb.min.mjs (previously lamb.esm.min.js).

Lamb it's also delivered on a CDN, courtesy of cdnjs, jsDelivr and unpkg:

<script src=""></script>
<script src=""></script>
<script src=""></script>

Please note that Lamb is served by jsDelivr since version 0.42.0.

You can try it right now in your browser, too.

Semantic Versioning.

Lamb uses semantic versioning and please be aware that, as long as the major version is 0, any bump in the minor version could involve a breaking change in the API. You can check the recent or the full changelog to see if your code is affected.

Frequently self-asked questions.

  • Is another JavaScript library really needed? Don't know, really. The story here is that I like to write my own code and, time permitting, to even reinvent the wheel: it's part of my learning process. This library is only a means for me to gather some utilities I wrote, clean them up a bit and put them together with some new tools to make a documented, reusable package.

  • Are your wheels rounder? Not at all, but I do try my best to add better suspension; and you do realise that you're reading a guy talking to himself, don't you?

  • Why you say "to help embracing functional programming"? Is it for beginners? No, it's a utility library for everyone; beginners included, though. Lamb embraces functional concepts and encourages users to take advantage of them, but without forcing anyone to change his style. Experienced functional programmers will feel immediately at home, and beginners will discover that the library is able to adapt to them while their knowledge grows.

  • Why ECMAScript 5? Because this is simply me tidying up some old code, and will hopefully be my goodbye to ES5 before fully diving into the world of transpilers.

  • What about ES4 environments? In my make-believe world they don't exist, but in case I can be proven wrong you can load some shims / polyfills before my library. There's plenty of those in the JavaScript Reference on MDN, and there are many pre-made packages as well out there.

  • Are there plans for the future? Absolutely yes: this isn't a complete work at all, only a first public release. I need better documentation and examples for starters, and I also want to add a bunch of other functions and concepts into the mix.

  • I really like Lamb's logo: are you the designer? I like it a lot too and, no, it isn't my doing: the author is a very talented designer who never signs his works by choice and doesn't want to be credited for it. Other than being eternally grateful, the least I can do is offer my services as a middleman and put you in touch if you need his craft.

  • Why "Lamb"? See the main header: because it's docile like a lamb. Lamb adapts to you without needing you to adapt.

Recent changes

You can also check the full changelog.

  • v0.60.0 - 2021/03/08

    • Fully compatible with version 0.59.0
    • Added mean, median and replace
  • v0.59.2 - 2020/07/17

    • Fully compatible with version 0.59.0
    • Updated "exports" property in package.json to address the issue where some tools couldn't access the manifest file. See
    • Got rid of ES5 in all examples
  • v0.59.0 - 2020/07/07

    • Sorry for all the renaming, but I'm in the process of freezing the API and wanted to tackle some inconsistencies in naming choices.
    • Updated to support Node.js ES modules (and renamed ES modules build to lamb.mjs)
    • Added split and splitBy
    • API change: renamed pick to pickIn and pickKeys to pick
    • API change: renamed skip to skipIn and skipKeys to skip
    • API change: renamed rename to renameIn and renameKeys to rename
    • API change: renamed pluck to pluckFrom and pluckKey to pluck
    • API change: renamed case to casus to avoid confusion and clashing with the switch statement's case
    • API change: renamed invoker and invokerOn to invoke and invokeOn
    • Fixed .DS_STORE file leaking again in the dist folder
  • v0.58.0 - 2019/06/18

    • Added one file ES modules build
    • API change: invoker now accepts an array of bound arguments
    • API change: benched immutable for the moment being
    • Added join and joinWith
    • Added findLast, findLastWhere, findLastIndex, findLastIndexWhere
    • Added dropLastWhile and takeLastWhile
    • Switched from uglify-js to terser
    • Updated docs, linting and tests
  • v0.57.0 - 2019/02/12

    • Splitted the library into ES modules
    • API change: sort, sortWith and sortedInsert now accept an array of sorters
    • API change: removed @@lamb/placeholder property as now the placeholder is exported as __
    • Switched to Jest as a test suite

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