这个js怎么实现

Question

写一个加法函数 sum，支持 sum(1)(2)(3,4)(5,6,7,...)

console.log(sum(1,2,3)(4)) // 输出 10

Answer 1

function sum(...args) {
  let total = args.reduce((t, v) => t + v, 0);
  const next = (...args) => {
    total += args.reduce((t, v) => t + v, 0);
    return next;
  }
  next.valueOf = () => total;
  return next;
}

因为是用valueOf实现最终值的输出，所以最取值时前面要带上+号

console.log(+sum(1,2,3)(4))

Answer 2

稍微优化一下 @asseek 的代码

function sum(...args) {
    let total = 0;
    const next = (...args) => {
        total += args.reduce((t, v) => t + v, 0);
        return next;
    }
    next.valueOf = () => total;
    return next(...args);
}

console.log(+sum(1, 2, 3)(4))
//[LOG]: 10