双语面试：实现一个组合函数

面试题 Interview Question

实现一个函数 compose，用于从右到左组合多个函数。
Implement a compose function that composes multiple functions from right to left.

要求 Requirements

1. compose(...fns) 接收多个函数作为参数
   compose(...fns) takes multiple functions as input
2. 返回一个新函数，该函数会按从右到左的顺序依次执行传入的函数
   Returns a new function that executes the passed-in functions from right to left
3. 支持任意数量的函数，且每个函数只能接收一个参数（即单参函数）
   Should support any number of unary functions (functions that take a single argument)
4. 不使用 this，保持纯函数式风格
   Must use pure functional programming style (no this)

参考答案 Reference Solution

function compose(...fns) {
  return function (initialValue) {
    return fns.reduceRight((acc, fn) => fn(acc), initialValue);
  };
}

示例 Example

const double = x => x * 2;
const square = x => x * x;

const composed = compose(square, double); // 相当于 square(double(x))

console.log(composed(3)); // 输出 Output: 36
// 解释：double(3) = 6，square(6) = 36

面试考察点 Interview Focus

• 对函数式编程核心概念（组合、管道、柯里化等）的理解
  Understanding of functional programming concepts like composition, piping, currying
• 对高阶函数、闭包、reduce 等的实际掌握
  Proficiency with higher-order functions, closures, and reduce