js函数聚合的三种实现方式

// 第一种：闭包存储，遍历执行
function compose1 (arr) {
    
  return (param) => {
    
    for (let fn of arr) {
    
      param = fn(param);
    }
    return param;
  }
}

// 第二种：递归嵌套，依次执行
function compose2 (arr) {
    
  return arr.length <= 1 ? arr[0] : (...args) => compose2(arr.slice(1))(arr[0](...args))
}

// 第三种：累加嵌套，依次执行，跟第二种相似
const compose3 = (arr) => arr.reduce((res, cur) => (...args) => cur(res(...args)));

function a (p) {
    
  return p + 1;
}
function b (p) {
    
  return p + 6;
}
function c (p) {
    
  return p * 2;
}

// 第四种：注意与第三章的区别
const compose4 = (arr) => arr.reduce((res, cur) => (...args) => res(cur(...args)));

const fn = compose4([a, b,c,d])
console.log(fn(1))