Takes several functions as argument and returns a function that is the juxtaposition of those functions.

Use Array.prototype.map() to return a fn that can take a variable number of args.
When fn is called, return an array containing the result of applying each fn to the args.

代码片段

const juxt = (...fns) => (...args) => [...fns].map(fn => [...args].map(fn));

使用样例

juxt(
  x => x + 1,
  x => x - 1,
  x => x * 10
)(1, 2, 3); // [[2,3,4],[0,1,2],[10,20,30]]

juxt(
  s => s.length,
  s => s.split(" ").join("-")
)("30 seconds of code"); // [[18],['30-seconds-of-code']]