const needs = ['wifi', 'shower', 'laundry']; const homes = [{ name: 'Home 1', wifi: 'y', shower: 'y', laundry: 'y', metro: 'n', balcony: 'y', fireplace: 'n', pool: 'y' }, { name: 'Home 2', wifi: 'n', shower: 'y', laundry: 'y', metro: 'n', balcony: 'n…

In this lesson, we'll filter a list of objects based on multiple conditions and we'll use Ramda's allPass function to create a joint predicate from multiple, individual predicate functions. const R = require('ramda'); const { allPass, propEq, lte, pr…

学习函数式编程的过程中,我接触到了 Ramda.js. 我发现,这是一个很重要的库,提供了许多有用的方法,每个 JavaScript 程序员都应该掌握这个工具. 你可能会问,Underscore 和 Lodash 已经这么流行了,为什么还要学习好像雷同的 Ramda 呢? 回答是,前两者的参数位置不对,把处理的数据放到了第一个参数. var square = n => n * n; _.map([4, 8], square) // [16, 64] 上面代码中,_.map的第一个参数[4, 8]…

When you want to build your logic with small, composable functions you need a functional way to handle conditional logic. You could wrap ternary expressions and if/else statements in functions, handling all of the concerns around data mutation yourse…

Promise chains can be a powerful way to handle a series of transformations to the results of an async call. In some cases, additional promises are required along the way. In cases where there are no new promises, function composition can reduce the n…

Naming things is hard and arguments in generic utility functions are no exception. Making functions "tacit" or "point free" removes the need for the extra parameter names and can make your code cleaner and more succinct. In this lesson…

We'll learn how to get a subset of an array by specifying items to include with filter, or items to exclude using reject. We'll also look at how to get the results from both filter and reject, neatly separated with partition. // we don't need to requ…

We'll learn how to take advantage of Ramda's automatic function currying and data-last argument order to combine a series of pure functions into a left-to-right composition, or pipeline, with Ramda's pipe function. A simple example will take 'teams'…

Ramda 基本的数据结构都是原生 JavaScript 对象,我们常用的集合是 JavaScript 的数组.Ramda 还保留了许多其他原生 JavaScript 特性,例如,函数是具有属性的对象. 今天我来说说javascript函数式的方法库--Ramda.Ramda主要特性如下: Ramda 强调更加纯粹的函数式风格.数据不变性和函数无副作用是其核心设计理念.这可以帮助你使用简洁.优雅的代码来完成工作. Ramda 函数本身都是自动柯里化的.这可以让你在只提供部分参数的情况下,轻松地在…

函数式编程是种编程方式,它将电脑运算视为函数的计算.函数编程语言最重要的基础是λ演算(lambda calculus),而且λ演算的函数可以接受函数当作输入(参数)和输出(返回值).和指令式编程相比,函数式编程强调函数的计算比指令的执行重要.和过程化编程相比,函数式编程里函数的计算可随时调用. 最近一直在研究函数式编程,从函数式编程中仿佛看到了js规范化的影子.大家都知道js是一门很灵活的编程语言,而这种灵活性在代码量的累积下会产生质量和可控性的问题.初学js的朋友大多都是结果导向,写的代码刚刚…

In this post, we are going to see how to use Ramda Lens. For example, we have data: const {log} = require('./lib/log'); const R = require('ramda'); const band = { name: 'K.M.F.D.M', members: { current: [ {name: 'Sascha Konictzko', plays: ['vocals', '…

0x00 何为函数式编程 网上已经有好多详细的接受了,我认为比较重要的有: 函数是"第一等公民",即函数和其它数据类型一样处于平等地位 使用"表达式"(指一个单纯的运算过程,总是有返回值),而不是"语句"(执行操作,没有返回值) 没有"副作用",即不修改外部值 0x01 开始函数式编程 在此之前,请先了解PHP中的匿名函数和闭包,可以参考我写得博客 函数式编程有两个最基本的运算:合成和柯里化. 函数合成 函数合成,即把多个函数…

Javascript's Object.assign is shadow merge, loadsh's _.merge is deep merge, but has probem for array. const person = { name: { first: "Joe" }, age: , color: "green", pets: ["dog", "lizard"] }; const update = { name:…

Sometimes you need to filter an array of objects or perform other conditional logic based on a combination of factors. Ramda's where function gives you a concise way to declaratively map individual predicates to object properties, that when combined,…

In this lesson we'll take a stateful React component and look at how we can refactor our setState calls to use an updater function and then leverage Ramda's evolvefunction to make our updater function a reusable utility that isn't tied to the React A…

In this lesson, we'll refactor a React component to use Ramda lenses to update our component state. We'll create a lens to focus on the property we want to target and use over to apply the existing state value to a utility function and we'll get back…

In this lesson we'll use a handful of Ramda's utility functions to take a queryString full of name/value pairs and covert it into a JavaScript object so we can access those properties in a more useful way. Along the way, we'll build up a composition…

We don't always control the data we need in our applications, and that means we often find ourselves massaging and transforming our data. In this lesson, we'll learn how to transform objects in a declarative way using ramda's evolve function. Assume…

Most of the functions offered by the ramda library are curried by default. Functions you've created or that you've pulled in from another library may not be curried. Ramda's curry and curryN functions allow you to take a non-curried function and use…

In this lesson we'll see how Ramda's path and pathOr functions can be used to safely access a deeply nested property from an object while avoiding the dreaded checks for undefined at each new property in the desired path. const R = require('ramda');…

In this lesson, we'll use Promise.all to get an array that contains the resolved values from multiple promises. Then we'll see how we can use Ramda to convert that array of values into a single object using zip with fromPairs. Then we'll refactor to…

In this lesson, we'll use Ramda's toPairs function, along with map, join, concatand compose to create a reusable function that will convert an object to a querystring. const R = require('ramda'); const {map, join, concat, compose, toPairs} = R; const…

In this lesson, we'll look at how we can use Ramda's invoker and constructNfunctions to take methods of an object and turn them into reusable utility functions that are curried and accept their object as the last argument. We'll convert a dot-chained…

In this lesson we'll take some existing code and refactor it using some functions from the Ramda library, most notably, compose and converge. When we're done, we'll have taken a function with a couple of local variables and parameter references and c…

When doing comparisons inside of functions, you end of relying heavily on the argument passed into the function. Ramda's converge allows you to do comparisons in a Point-Free style allowing you more flexibility with composing and constructing functio…

You can really unlock the power of ramda (and functional programming in general) when you combine functions. Counting words in a string may seem like a relatively difficult task, but ramda makes it easy by providing a countBy function. This lesson wa…

The difference between sort, sortBy, sortWith is that: 1. sort: take function as args. 2. sortBy: take prop as args. 3. sortWith: take array of funcs as args. const R = require('ramda'); const {sort, sortBy, sortWith, descend, prop, ascend} = R; cons…

In this lesson we'll take an array of objects and map it to a new array where each object is a subset of the original. We'll look at multiple ways to accomplish this, refactoring our code into a simple and easy to read function using Ramda's map, pic…

So what is Point-free function. Take a look this example: const getUpdatedPerson = (person) => R.assoc('avatar', getUrlFromPerson(person), person); To make it as point-free function, we need to get rid of person object we pass into the function. Firs…

In this lesson we'll learn the basics of using lenses in Ramda and see how they enable you to focus changes on specific properties of an object while keeping your data immutable. what 'R.lens' do is able to get or set prop value but keep the object i…