[Ramada] Build a Functional Pipeline with Ramda.js

时间：2016-08-24 06:36:20 阅读：339 评论：0 收藏：0 [点我收藏+]

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‘ array and output the best score team‘s name. We use ‘R.sort‘, ‘R.head‘ and ‘R.prop‘ to get job done:

const teams = [
  {name: ‘Lions‘, score: 5},
  {name: ‘Tigers‘, score: 4},
  {name: ‘Bears‘, score: 6},
  {name: ‘Monkeys‘, score: 2},
];

const getTopName = function(teams){
  const sorted = R.sort( (a,b) => b.score > a.score, teams);
  const bestTeam = R.head(sorted);
  const name = R.prop(‘name‘, bestTeam);
  return name;
}

const result = getTopName(teams)
console.log(result)

One thing in Ramda which is really cool that, for example, ‘R.sort‘ takes two arguements, if you don‘t passin the second arguement which is ‘teams‘, it will then return a function, so that it enable you currying function and take second arguement as param.

const teams = [
  {name: ‘Lions‘, score: 5},
  {name: ‘Tigers‘, score: 4},
  {name: ‘Bears‘, score: 6},
  {name: ‘Monkeys‘, score: 2},
];


const getBestTeam = R.sort( (a,b) => b.score > a.score);
const getTeamName = R.prop(‘name‘);
const getTopName = function(teams){
  const sorted = getBestTeam(teams);
  const bestTeam = R.head(sorted);
  const name = getTeamName(bestTeam);
  return name;
}

const result = getTopName(teams)
console.log(result)

We will still get the same result.

Use ‘R.pipe‘ to chain function together

In functional programming or lodash (_.chain), we get used to write chain methods, in Ramda, we can use R.pipe():

const teams = [
  {name: ‘Lions‘, score: 5},
  {name: ‘Tigers‘, score: 4},
  {name: ‘Bears‘, score: 6},
  {name: ‘Monkeys‘, score: 2},
];


const getBestTeam = R.sort( (a,b) => b.score > a.score);
const getTeamName = R.prop(‘name‘);
const getTopName = R.pipe(
  getBestTeam,
  R.head,
  getTeamName
);

/*
const getTopName = function(teams){
  const sorted = getBestTeam(teams);
  const bestTeam = R.head(sorted);
  const name = getTeamName(bestTeam);
  return name;
}*/

const result = getTopName(teams)
console.log(result)

[Ramada] Build a Functional Pipeline with Ramda.js

原文：http://www.cnblogs.com/Answer1215/p/5801424.html

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