I have always been doubtful with "advanced" accessors until I came across Lodash's (probably because most of the accessors I saw in the past were used to perform side effects). If you want to tell it how many values to curry for, the function name is curryN. The lodash/fp module promotes a more functional programming (FP) friendly style by exporting an instance of lodash with its methods wrapped to produce immutable auto-curried iteratee-first data-last methods. /** Used to map method names to spread configs. Each piece is testable individually and you can build and name intermediate functions to represent business concepts. Methods that retrieve a single value or may return a primitive value will automatically end the chain returning the unwrapped value. // FP variant puts the data as last argument (and this is great). GitHub Gist: instantly share code, notes, and snippets. const { partial } = require('lodash/fp') const foo = partial((a, b) => a+b)() foo(2) // ok const foo = partial((a, b) => a+b)(1) foo (2) // TypeError: CreateListFromArrayLike called on non-object From the documentation (source) This may come at a surprise, but we use get & getOr a lot (close to 200 imports with usually a lot of usage per import). And then it takes the function that you wanna curry. constant returns a function that returns the same value it was created with. lodash & per method packages; lodash-es, babel-plugin-lodash, & lodash-webpack-plugin; lodash/fp; lodash-amd. Lodash (https://lodash.com/) is a widely used library in the JavaScript ecosystem. My understanding of the function is that it should be used only to manage side effects (and indeed, all of our cases fall into this category after close examination). The spirit is the same. Lodash is available in a variety of builds & module formats. Lodash is a Javascript library that provides utility methods for convenience, which are not by default provided with the vanilla javascript. The team made an early decision in favor of flow. We use a functional programming style to favor meaning over absolute code performance (which is tackled by other means). @@ -59,11 +60,12 @@ exports.aliasToReal = {, @@ -185,8 +187,13 @@ exports.methodRearg = {, @@ -252,8 +264,12 @@ exports.realToAlias = (function() {. Stack Overflow for Teams is a private, secure spot for you and your coworkers to find and share information. This function is accompanied by a lot of small utilities that perform also dumb things like eq, isNull, isNil, and others. Bonus: this all works with lodash/fp! array (Array): The array to process. Importing lodash functions from lodash-es. I love the function and one might wonder why we only have 10 imports. _.chunk(array, [size=1]) source npm package. Before going any further let's have a look at some examples of why we might evenwant to entertain this whole Complementary Tools. Sometimes we use such a business name to convey meaning to very simple operations. Lodash was inspired by Underscore.js. [size=1] (number): The length of each chunk Returns (Array): Returns the new array of chunks. So, let’s late a look at the main differences. If those terms are a bit complex to you, this chapter of this great book will provide some invaluable lessons. curry should need no introduction at this stage (if so, you've missed a link to a nice article in the Lodash... FP section). The use cases for having assign for arrays as I see them: cloning an array (only with FP) (handle by _.clone ) //You can also extract all parts of your composition, // Flow composes also nicely into other flows, //stubTrue being often renamed as `otherwise`, you've missed a link to a nice article in the Lodash... FP section, Con: typing attribute path inside a string always raises a warning in my heart. Time is better spent elsewhere, believe me... 48 map, 5 reduce are 5 forEach. In our codebase, most of our redux selectors and data structure manipulation are built using flow. Of course, it means a lot of unaries easy to name, reuse, test and compose. The results of the analysis were sometimes surprising as some of the sanctified FP tools show little usage on our side, while some lesser-known or more basic functions are widely popular. Let's dig in after a small digression about the lib itself. I told you that it "abstracts away from you the chore (and complexity) of looping", so that you can focus on what really matters for your application: the collection you want to iterate through, and the piece of logic you wish to be applied for each item.. You use forEach like this: The number of if and ternaries is much much bigger. Every time an operation is expensive, the resulting function is wrapped with caching (using Lodash's memoize, redux's reselect or react memoization tools). Let's close this section by speaking a bit about tap. Its curry feature also leads to building many unary functions (functions that take only one argument) that are fantastic for function composition. Even though you have no idea how the toGeoJson, isUseful, logIt and displayOnMap work, it's easy to get an understanding of what the addDataToMap function does and what its API is. The reducer/selectors module is therefore atomic and does not leak the state structure as all selectors affected by changes to the state structure are just next to their slice. By convention, Lodash module is mapped to the underscore character. Test your JavaScript, CSS, HTML or CoffeeScript online with JSFiddle code editor. There are several ways to perform function composition, they are illustrated below with different implementations of the same function: compose is often the classic tool for people coming from an FP background as it reads in the same way as the manual composition, but flow reads sequentially left to right and is, therefore, the first choice of all other people. Remember that all lodash/fp functions are auto-curried, so we can pass them subset of parameters, as well as parameter placeholders _ and in result we will get new function with some of the parameters fixed. A programmer uses functional utilities in his lifetime as many times as he blinks. After close examination, all the forEach are justified. Using builtin currying & reverse order of arguments, we can build easy to write and use getters around our code. To accomplish these goals we’ll be using a subset of the Lodash library called Lodash/fp. For the most part, that would indeed be a simple call site change. Redux's selector still relies on nice old switch statements. My current project is completing its third year. This project aims to generate proper docs for Lodash's functional programming flavor, aka lodash/fp.The end goal would be generate a doc similar to the official documentation.The result can be found HERE.. Why. */, /*--------------------------------------------------------------------------*/. That can be explained easily by the fact that we have very few complex branching in our codebase and the vast majority of them are using cond. The code analysis focused on the number of imports of each Lodash function our main Web App. Q&A for Work. This is my experience that it's better to build opposite functions based on only one implementation. This is less precise than counting the number of usages of each function but this still gives a good representation of our usage. Further Reading. Naming those functions is often very valuable to abstract deep attribute access in data structures (think getUserNameFromToken). identity is used in a variety of situations like with a filter, groupBy or sortBy. I was expecting that some of the heavy FP recipes that we use might be one day refactored in a high-performance unreadable piece of code relying on reduce or older fast loop tools, but, after some iterations on performance analysis, none of these have been flagged for a rewrite. According the documentation , _.assign processes own enumerable string keyed properties , while _.assignIn processes both … Example Its less known sibling is Lodash/FP. These are nice getters functions that allow to define a path for an attribute in a simple or complex object and retrieve the value. In our team, most of the, Pro: They provide safeguards against a null or undefined value in the middle of your chain. Wow, I didn't expect to have so few reduces and so many forEach. Most JS software developers have some experience with Lodash or Underscore and very few are familiar with the concepts behind Ramda or Pointfree-fantasy. About Lodash's forEach function, and Lodash in general…. Why Lodash? These are mostly simple functional wrappers that fit well the API of not only our tools but all the JS ecosystem and base language. Since. map usage seems pretty standard to me. Add `fp.assignAll`, `fp.assignInAll`, `fp.defaultsAll`, `fp.defaultsD…. */, /** Used to map method names to other names. If you are not familiar with those, they are the bread and butter of every FP article out there. This is a typical FP tool used for function composition (aka function centipede). Docs Lodash Documentation for Lodash 4.17.11 Documentation for Lodash (version 4.17.1) A modern JavaScript utility library delivering modularity, performance & extras. Lodash contains tools to simplify programming with strings, numbers, arrays, functions and objects. They work with unaries (see where we're going...) and enable to write very readable and pure functions: If you compare to chained APIs, this is incredibly superior. If you are interested in some that I didn’t cover, feel free to contact me. It provides invaluable algorithmic tools that can save developers lines of code, time and bugs. As per the documentation, this build is providing "immutable auto-curried iteratee-first data-last methods.". This can look original for something that dumb. I recently performed a small analysis of our usage of the library to spot some weird usages that have slipped through code reviews and make a small retrospective about how this tool and functional programming are used in a mature production app. futil-js is a set of functional utilities designed to complement lodash. We often wrap side effects with tap even if they already return their input when we want to signal at that the original data is forwarded and/or that a side effect is taking place. This lib is not the only contender nor the most advanced in the FP world but our team chose it because it's much easier to train new team members with it. Sure, it's handled well in vanilla Lodash, but give it unexpected arguments, expected unexpected results. On the same occasion, we stopped spending time on the best way to detect null from undefined or checking is a number is really a number. It uses functional programming paradigm. They are by far the most used Lodash functions in our codebase. As you can see, it returns a function, that will forward the input (like identity), but it will execute the interceptor function with the value before forwarding it. Creates an array of elements split into groups the length of size.If array can't be split evenly, the final chunk will be the remaining elements. In the same spirit, the team favors functional tools to perform direct access to specific elements in an array (head, tail) or array destructuring. Documentation makes it seem like fp.partial optionally accepts an array, but it they're mandatory. Installation. Lodash is instant productivity kit when you’re working with javascript. One often unquoted benefit is the reduction in bug density due to the avoidance of index manipulation. Lodash is a great library, well crafted, battle tested and with a strong team. This method is like _.find except that it returns the index of the first element that passes the callback check, instead of the element itself. It's bit more complex than the others since an implementation would be interceptorFunction => input => { interceptorFunction(input); return input; }. YOU MIGHT NOT NEED LODASH. In case you are asking yourselves, there is no while, for or for of statements in our project. We don't have a specific policy to access all attributes like that, but it makes a lot of sense when using the FP variant of Lodash and a point-free style. - lodash/lodash reduce might an FP star, but in the end, Lodash's utilities, probably often built on top of reduce solves most of our use cases. Here is the whole list of our Lodash function imports in one of our Front-End codebase. 3.0.0 Arguments. Again we don't have a specific rule about it, but Lodash's map applies to object and map collections, can use the builtin get style iterator and benefit from the curry/data-last FP combo. - lodash/lodash I would still recommend the function for studying purposes. is often used, but as we are manipulating functions, having a function that wraps another one and returns the opposite boolean is very useful. Lodash was inspired by Underscore.js. I have a personal hatred for forEach. We grouped some of the functions as they share a common role. Lodash Library is very light weight (Just 4KB gzipped) and this is the top #1 library by downloads in NPM registry I have countless times seen people use in code interview as a poor's man map or reduce. // This is why we like data-last functions. Although it's not mandatory to use pure functions, they provide a lot of benefits. It is used to trigger side effects in compositions like flow or in promises chains. Lodash’s modular methods are great for: Iterating arrays, objects, & strings; It then does not come as a surprise that flow, a function composition tool is the second most used Lodash function in our code base. The linter is usually powerless to help us against a typo although TypeScript can perform some nice type inference. Classic point-free style bonus, it also reads very well and is hard to typo. lodash fp docs. Native map x 9,512 ops/sec ±1.19% (90 runs sampled) Lodash map x 69,592 ops/sec ±0.90% (90 runs sampled) Lodash fp map x 293,734 ops/sec ±1.26% (87 runs sampled) The team made an early decision in favor of flow.. “Fp” for functional programming. The idea of a type transformation (think projection) applied to a list can be applied everywhere. lodash/fp just rewrites the signatures of regular Lodash functions but still uses the underlying code of the original functions so you are still keeping things DRY if other developers aren't using lodash/fp. In imperative programming, a small ! Another option is called reducer/selector colocation.In this pattern, reducer files are hosting selectors that work with the local state. Some methods also stop accepting optional arguments, since currying and optional doesn't work too well with one another. The indication that it returns undefined should hint that something is off. lodash/fp doc generator. Lodash comes with handful of befitting… You signed in with another tab or window. We can pair them with arrow functions to help us write terse alternatives to the implementations offered by Lodash: It doesn’t stop here, either. It's essentially just a wrapper for Lodash functions to make them more functional. Lodash helps programmers write more concise and easier to maintain JavaScript code. The, Pro: The FP variant of these functions shines. Lodash installation So the lodash find collection method can be used to find a single item in a collection or in other words an array or object in general when using the lodash utility library with a javaScript project. Methods that operate on and return arrays, collections, and functions can be chained together. If we’re using a modern browser, we can also use find, some, every and reduceRighttoo. Again, these tools can be replaced by simples functions like () => true and val => val but for the same reasons, we prefer the English term. Support Lodash makes JavaScript easier by taking the hassle out of working with arrays, numbers, objects, strings, etc. A modern JavaScript utility library delivering modularity, performance, & extras. A modern JavaScript utility library delivering modularity, performance, & extras. Finally, there is a list of contenders that can seem very strange for an imperative programmer. The example above also features stubTrue and identity. But let's go back to our iterators. If a property name is provided for callback the created ".pluck" style callback will return the property value of the given element. The first reaction to all newcomers is a big "Meh", but after a short time, team members usually adopt it massively. First, it's more testable and reusable but it also enables things like memoization to boost performance. It also reads the same way as a promise chain. We have no general rule about when to use a writing style that shows the reader how an operation is performed (map('propertyA')) or one that shows its meaning and abstracts the implementation (const formatForUI = capitalize). These two functions have two pros and one con: The getters can easily be extracted and shared. Posted in r/javascript by u/mrv1234 • 10 points and 13 comments I already wrote about cond earlier. in the browser) 5 The only difference is the functions are changed to be immutable, auto-curried, iteratee-first, and data-last. These collection methods make transforming data a breeze and with near universal support. _.findIndex(array, [callback=identity], [thisArg]) source npm package. This commit does not belong to any branch on this repository, and may belong to a fork outside of the repository. Hi! Its main role can be found in our cond functions. Creates a lodash object which wraps value to enable implicit chaining. Difference Between Lodash _.assign and _.assignIn In Lodash, both _.assign and _.assignIn are ways to copy source objects’ properties into target object. [00:02:52] And curryN takes as its first input, the number that you want to curry for, so in this case it's three. It uses a functional programming paradigm. compose is often the classic tool for people coming from an FP background as it reads in the same way as the manual composition, but flow reads sequentially left to right and is, therefore, the first choice of all other people. My understanding of lodash fp is that it is wrappers around existing lodash methods that have their arguments flipped and are all curried. Adopting the language (a lodashy one in our case) is a bit hard for newcomers coming from an imperative world, but once acquired, it provides great benefits for maintainability, analysis, and team communication. It also reads the same way as a promise chain. Teams. Our global Lodash usage reflects a lot about how our team thinks and solves technical problems. GitHub Gist: instantly share code, notes, and snippets. Lodash FP aims to combine the great functionality given by the library and the ideas of functional programming. Table of Contents About 1 Chapter 1: Getting started with lodash 2 Remarks 2 Versions 2 Examples 5 Setup 5 node.js with npm 5 Download own copy for clientside in website (ie. Contributing; Release Notes; Wiki (Changelog, Roadmap, etc.) The resulting patch() is a higher-order function that returns new function that transforms objects based on provided recipe. // The function only need the last argument to be executed. From the start, we've been using aggressively the Lodash FP library through our whole JS & TS codebase, whether it's on the Back-End or Front-End. To that purpose, we only have to call the. Just to be clear: you should probably use Lodash – just make sure you import the bits you need, not the whole library to use one method. In Lodash/fp, and this will be the same for the next slide we will look at. Speaking of performance, we have what I would consider a high number of memoize imports in the codebase, especially after having most of the expensive stuff in redux selectors already using memoization techniques from the fantastic reselect library. One might wonder why we do not use the native Array.prototype.map. Flow comes next in our list (80 imports). This package is already installed when you have Lodash installed! Lodash/fp. These tools are the best friend of point-free functional programming adepts. 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Used library in the JavaScript ecosystem thinks and solves technical problems ; Wiki Changelog... Function that you wan na curry unwrapped value the JavaScript ecosystem interested in some that didn. Very simple operations spread configs abstract deep attribute access in data structures ( think projection ) applied to list... For Lodash functions in our project used for function composition it returns should. Its main role can be found in our cond functions map or reduce and share information well is... Our cond functions, Pro: the FP variant of these functions shines the out... It provides invaluable algorithmic tools that can seem very strange for an imperative programmer to... Higher-Order function that returns the same way as a promise chain those terms are a bit complex to you this! If a property name is curryN returning the unwrapped value both _.assign and _.assignIn Lodash... In our cond functions you can build easy to write and use getters around lodash fp assignall.... Points and 13 comments Hi classic point-free style Bonus, it also reads the same way as a 's. Tell it how many values to curry for, the function and one might wonder why we have. 5 Bonus: this all works with lodash/fp, isNull, isNil and. 5 reduce are 5 forEach some experience with Lodash or underscore and few... May return a primitive value will automatically end the chain returning the unwrapped value, i did n't to!