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 converted it into more streamlined "point-free" or "tacit" functions.

For example, we have following function:

const R = require('ramda');

const person = {
id: ,
name: 'Joe'
}; const generateUrl = (id) => `http://img.soicalnetwork.com/avatar/${id}.png`;
const getUpdatedPerson = (person) => {
const url = generateUrl(person.id);
return R.assoc('avatar', url, person);
}
const result = getUpdatedPerson(person);

It will add a 'avatar' prop to person object.

We want to refactor the code to make it point free style, we the functions can be more reuseable and easy to understand.

First try:

//===============================================
// #1 Refactoring
//===============================================
/*
Solve the problem that when id is undefined, we need a default image
Solution: propOr('defaultValue', 'prop')
*/ const generateUrl = (id) => `http://img.soicalnetwork.com/avatar/${id}.png`;
const getUpdatedPerson = (person) => {
const url = generateUrl(R.propOr('default', 'id')(person));
return R.assoc('avatar', url, person);
}
const result = getUpdatedPerson(person);
console.log(result);

Here we use 'R.propOr', to get prop of an object and set default fallback value. This can help us prevent undefined problem.

Second try:

//===============================================
// #2 Refactoring
//===============================================
/**
* Extra a single function to get Person url.
* Solution: Here we using R.compose.
* SO getURLFromPerson is point-free function.
*/ const generateUrl = (id) => `http://img.soicalnetwork.com/avatar/${id}.png`;
const getURLFromPerson = R.compose(
generateUrl,
R.propOr('default', 'id')
);
const getUpdatedPerson = (person) => R.assoc('avatar', getURLFromPerson(person), person);
const result = getUpdatedPerson(person);
console.log(result);

Here we use 'R.compose' to make 'getURLFromPerson' as a point-free function. Notice in the function, we no longer need to pass 'person' object as a param.

Third try:

//===============================================
// #3 Refactoring
//===============================================
/**
* In getUpdatedPerson function, we still relay on the 'person' param we pass in.
* We want to make it a point-free function also.
* Solution: we can use R.converge
*/
const generateUrl = (id) => `http://img.soicalnetwork.com/avatar/${id}.png`;
const getURLFromPerson = R.compose(
generateUrl,
R.propOr('default', 'id')
);
// const getUpdatedPerson = (person) => R.assoc('avatar', getURLFromPerson(person), person);
const getUpdatedPerson = R.converge(
R.assoc('avatar'),
[
getURLFromPerson,
R.identity
]
)
const result = getUpdatedPerson(person);
console.log(result);

The old verson of 'getUpdatedPerson' relay on 'person' param, to make it as point-free function style, we can use another way 'R.converge'.

[Ramda] Refactor to Point Free Functions with Ramda using compose and converge的更多相关文章

  1. [Ramda] Curry and Uncurry Functions with Ramda

    Most of the functions offered by the ramda library are curried by default. Functions you've created ...

  2. [Ramda] Get Deeply Nested Properties Safely with Ramda's path and pathOr Functions

    In this lesson we'll see how Ramda's path and pathOr functions can be used to safely access a deeply ...

  3. [Ramda] Convert Object Methods into Composable Functions with Ramda

    In this lesson, we'll look at how we can use Ramda's invoker and constructNfunctions to take methods ...

  4. [Ramda] Refactor to a Point Free Function with Ramda's useWith Function

    Naming things is hard and arguments in generic utility functions are no exception. Making functions ...

  5. [Ramda] Refactor a Promise Chain to Function Composition using Ramda

    Promise chains can be a powerful way to handle a series of transformations to the results of an asyn ...

  6. [Ramda] Eliminate Function Arguments (Point-Free Style) with Ramda's Converge

    When doing comparisons inside of functions, you end of relying heavily on the argument passed into t ...

  7. [Ramda] Count Words in a String with Ramda's countBy and invert

    You can really unlock the power of ramda (and functional programming in general) when you combine fu ...

  8. [React] Update Component State in React With Ramda Lenses

    In this lesson, we'll refactor a React component to use Ramda lenses to update our component state. ...

  9. [Ramda] Pick and Omit Properties from Objects Using Ramda

    Sometimes you just need a subset of an object. In this lesson, we'll cover how you can accomplish th ...

随机推荐

  1. Spring学习总结(5)——IOC注入方式总结

    一.构造注入 在类被实例化的时候,它的构造方法被调用并且只能调用一次.所以它被用于类的初始化操作.<constructor-arg>是<bean>标签的子标签.通过其<v ...

  2. CSS3制作W3cplus的关注面板

    <!DOCTYPE HTML> <html lang="en-US"> <head> <meta charset="UTF-8& ...

  3. SQLite-SQLiteDatabase 数据库实例练习

    今天趁着有时间,自己在网上找了相关的数据库操作代码,进行了一下练习,先上代码 main.xml文件 <RelativeLayout xmlns:android="http://sche ...

  4. JavaScript篇(一)二叉树的插入 (附:可视化)

    一.二叉树概念 二叉树(binary tree)是一颗树,其中每个节点都不能有多于两个的儿子. 字节一面,第一道就是二叉树的插入,在这里其实是对于一个二叉查找树的插入. 使二叉树成为二叉查找树的性质是 ...

  5. angular设置全局变量,可修改监听变量

    创建service.module.ts import { NgModule, ModuleWithProviders } from '@angular/core'; import { SomeShar ...

  6. Mongodb总结5-通过装饰模式,用Mongodb解决Hbase的不稳定问题

    最近继续学习Mongodb的根本原因,是为了解决今天的问题.项目中用到了Hbase,生产环境服务器用了3台,但是不够稳定,每2天左右,就连不上了.重启就好了,当然,这是一个历史遗留问题.我在想,是不是 ...

  7. 洛谷——P1046 陶陶摘苹果

    https://www.luogu.org/problem/show?pid=1046 题目描述 陶陶家的院子里有一棵苹果树,每到秋天树上就会结出10个苹果.苹果成熟的时候,陶陶就会跑去摘苹果.陶陶有 ...

  8. Windows 7 下快速挂载和分离VHD文件的小脚本

    1.保存以下代码为VDM.vbs,放在Windows\system32下 Dim ArgsSet Args = WScript.ArgumentsTranArgs = " "For ...

  9. (转)bat批处理的注释语句

    在批处理中,段注释有一种比较常用的方法: goto start = 可以是多行文本,可以是命令 = 可以包含重定向符号和其他特殊字符 = 只要不包含 :start 这一行,就都是注释 :start 另 ...

  10. 【CS Round #48 (Div. 2 only)】Game of Chance

    [链接]h在这里写链接 [题意] 在这里写题意 [题解] 在这里写题解 [错的次数] 0 [反思] 在这了写反思 [代码] #include <bits/stdc++.h> using n ...