The use cases for having assign for arrays as I see them: cloning an array (only with FP) (handle by _.clone ) // This is why we like data-last functions. Q&A for Work. Lodash installation 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). In case you are asking yourselves, there is no while, for or for of statements in our project. A modern JavaScript utility library delivering modularity, performance, & extras. These two functions have two pros and one con: The getters can easily be extracted and shared. Finally, there is a list of contenders that can seem very strange for an imperative programmer. _.findIndex(array, [callback=identity], [thisArg]) source npm package. Every time an operation is expensive, the resulting function is wrapped with caching (using Lodash's memoize, redux's reselect or react memoization tools). First, it's more testable and reusable but it also enables things like memoization to boost performance. A modern JavaScript utility library delivering modularity, performance, & extras. 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. So, let’s late a look at the main differences. The, Pro: The FP variant of these functions shines. In Lodash/fp, and this will be the same for the next slide we will look at. 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. // The function only need the last argument to be executed. Importing lodash functions from lodash-es. About Lodash's forEach function, and Lodash in general…. To that purpose, we only have to call the. To accomplish these goals we’ll be using a subset of the Lodash library called Lodash/fp. These collection methods make transforming data a breeze and with near universal support. Documentation makes it seem like fp.partial optionally accepts an array, but it they're mandatory. Naming those functions is often very valuable to abstract deep attribute access in data structures (think getUserNameFromToken). 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. The team made an early decision in favor of flow. Bonus: this all works with lodash/fp! Each piece is testable individually and you can build and name intermediate functions to represent business concepts. If you are interested in some that I didn’t cover, feel free to contact me. Lodash FP aims to combine the great functionality given by the library and the ideas of functional programming. I already wrote about cond earlier. They are by far the most used Lodash functions in our codebase. 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. Sometimes we use such a business name to convey meaning to very simple operations. 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. This can look original for something that dumb. /** Used to map method names to spread configs. Lodash’s modular methods are great for: Iterating arrays, objects, & strings; The indication that it returns undefined should hint that something is off. It uses a functional programming paradigm. Although it's not mandatory to use pure functions, they provide a lot of benefits. Its less known sibling is Lodash/FP. - lodash/lodash 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) As per the documentation, this build is providing "immutable auto-curried iteratee-first data-last methods.". Some methods also stop accepting optional arguments, since currying and optional doesn't work too well with one another. It provides invaluable algorithmic tools that can save developers lines of code, time and bugs. Classic point-free style bonus, it also reads very well and is hard to typo. Redux's selector still relies on nice old switch statements. If those terms are a bit complex to you, this chapter of this great book will provide some invaluable lessons. _.chunk(array, [size=1]) source npm package. My understanding of lodash fp is that it is wrappers around existing lodash methods that have their arguments flipped and are all curried. These are nice getters functions that allow to define a path for an attribute in a simple or complex object and retrieve the value. 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. Stack Overflow for Teams is a private, secure spot for you and your coworkers to find and share information. In our codebase, most of our redux selectors and data structure manipulation are built using flow. It also reads the same way as a promise chain. negate is our fifth most imported Lodash function. Installation. Most JS software developers have some experience with Lodash or Underscore and very few are familiar with the concepts behind Ramda or Pointfree-fantasy. Lodash is instant productivity kit when you’re working with javascript. Flow comes next in our list (80 imports). 3.0.0 Arguments. Lodash contains tools to simplify programming with strings, numbers, arrays, functions and objects. [size=1] (number): The length of each chunk Returns (Array): Returns the new array of chunks. lodash & per method packages; lodash-es, babel-plugin-lodash, & lodash-webpack-plugin; lodash/fp; lodash-amd. And then it takes the function that you wanna curry. Its curry feature also leads to building many unary functions (functions that take only one argument) that are fantastic for function composition. 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. Let's dig in after a small digression about the lib itself. Lodash (https://lodash.com/) is a widely used library in the JavaScript ecosystem. - lodash/lodash Example Lodash was inspired by Underscore.js. lodash fp docs. 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. Lodash helps programmers write more concise and easier to maintain JavaScript code. In our team, most of the, Pro: They provide safeguards against a null or undefined value in the middle of your chain. 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 … 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. 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. I have a personal hatred for forEach. It's essentially just a wrapper for Lodash functions to make them more functional. If a property name is provided for callback the created ".pluck" style callback will return the property value of the given element. is often used, but as we are manipulating functions, having a function that wraps another one and returns the opposite boolean is very useful. By convention, Lodash module is mapped to the underscore character. 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. This package is already installed when you have Lodash installed! Docs Lodash Documentation for Lodash 4.17.11 Documentation for Lodash (version 4.17.1) A modern JavaScript utility library delivering modularity, performance & extras. Again, these tools can be replaced by simples functions like () => true and val => val but for the same reasons, we prefer the English term. The code analysis focused on the number of imports of each Lodash function our main Web App. In the same spirit, the team favors functional tools to perform direct access to specific elements in an array (head, tail) or array destructuring. The spirit is the same. // Here we put the currying into practice to build a getter function. 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. 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. 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. Lodash comes with handful of befitting… 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. It can easily be replaced by a small arrow function like () => 2 but it for me it reduces the cognitive load to have plain English instead of a function expression and helps when talking about code. Teams. // FP variant puts the data as last argument (and this is great). For the most part, that would indeed be a simple call site change. Lodash is a great library, well crafted, battle tested and with a strong team. @@ -59,11 +60,12 @@ exports.aliasToReal = {, @@ -185,8 +187,13 @@ exports.methodRearg = {, @@ -252,8 +264,12 @@ exports.realToAlias = (function() {. We grouped some of the functions as they share a common role. 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). Pro: the array to process map method names to spread configs and very few are with... Return a primitive value will automatically end the chain returning the unwrapped value take only one.. Main role can be chained together would indeed be a simple call site change this gives! Both _.assign and _.assignIn are ways to copy source objects ’ properties target... 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