This function is accompanied by a lot of small utilities that perform also dumb things like eq, isNull, isNil, and others. Another option is called reducer/selector colocation.In this pattern, reducer files are hosting selectors that work with the local state. 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. 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). 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. 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). Since. [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. The use cases for having assign for arrays as I see them: cloning an array (only with FP) (handle by _.clone ) In Lodash/fp, and this will be the same for the next slide we will look at. Lodash makes JavaScript easier by taking the hassle out of working with arrays, numbers, objects, strings, etc. 3.0.0 Arguments. 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. If we’re using a modern browser, we can also use find, some, every and reduceRighttoo. Of course, it means a lot of unaries easy to name, reuse, test and compose. @@ -59,11 +60,12 @@ exports.aliasToReal = {, @@ -185,8 +187,13 @@ exports.methodRearg = {, @@ -252,8 +264,12 @@ exports.realToAlias = (function() {. 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. 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. 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 & per method packages; lodash-es, babel-plugin-lodash, & lodash-webpack-plugin; lodash/fp; lodash-amd. YOU MIGHT NOT NEED LODASH. Let's dig in after a small digression about the lib itself. lodash/fp doc generator. It's bit more complex than the others since an implementation would be interceptorFunction => input => { interceptorFunction(input); return input; }. Methods that retrieve a single value or may return a primitive value will automatically end the chain returning the unwrapped value. According the documentation , _.assign processes own enumerable string keyed properties , while _.assignIn processes both … I have countless times seen people use in code interview as a poor's man map or reduce. 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). Some methods also stop accepting optional arguments, since currying and optional doesn't work too well with one another. A programmer uses functional utilities in his lifetime as many times as he blinks. I already wrote about cond earlier. 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. */, /** Used to map method names to other names. Again, these tools can be replaced by simples functions like () => true and val => val but for the same reasons, we prefer the English term. 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. The linter is usually powerless to help us against a typo although TypeScript can perform some nice type inference. One might wonder why we do not use the native Array.prototype.map. My current project is completing its third year. 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) In the same spirit, the team favors functional tools to perform direct access to specific elements in an array (head, tail) or array destructuring. Every time an operation is expensive, the resulting function is wrapped with caching (using Lodash's memoize, redux's reselect or react memoization tools). The number of if and ternaries is much much bigger. 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. Here is the whole list of our Lodash function imports in one of our Front-End codebase. Redux's selector still relies on nice old switch statements. 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