JavaScript函数式编程之组合函数

1.Reduce

过程是一个函数 pipeline,参数组合+函数pipeline

JavaScript 函数式编程实践指南 - 修言 - 掘金小册

const arr = [1, 2, 3]
const initialValue = 0  
const add = (previousValue, currentValue) =>previousValue+currentValue;
//执行顺序 0 + 1 + 2 + 3  
const sumArr = arr.reduce(add,0); 
console.log(sumArr) //expected output: 6

执行过程：

2.map

function add1AndPush(previousValue, currentValue) {
  // previousValue 是一个数组
  previousValue.push(currentValue + 1)
  return previousValue
}
const arr = [1,2,3]
const newArray = arr.map((num)=> num+1)
const newArray1 = arr.reduce(add1AndPush,[])
console.log(newArray);//[2, 3, 4]
console.log(newArray1);//[2, 3, 4]

3.compose

 4.pipe