Desugared map from https://blog.benestudio.co/pattern-matching-in-javascript-es6-10fff60aae79

desugaredmap.es

//Original:
//
//const map = (f, [x, …xs]) => (
// (x === undefined && xs.length === 0) ? []
// : [f(x), …map(f, xs)]
//);

const map=(f,array)=>{
  const iterator=array[Symbol.iterator]()
  let {done,value}=iterator.next()
  let x=value
  let xs=[]
 ;({done,value}=iterator.next())
  while(!done){
    xs[xs.length]=value
   ;({done,value}=iterator.next())}
  if('return' in iterator)
    iterator.return()
  return (x===undefined && xs.length===0)
   ?[]
   :[f(x),...map(f, xs)]}

console.log(map(e=>2**e,[0,1,2,3,4,5,6,7,8,9]))

//Testing in the EcmaScript shells I have installed:
//> ch desugaredmap.es
//  1,2,4,8,16,32,64,128,256,512
//> js desugaredmap.es
//  1,2,4,8,16,32,64,128,256,512
//> node desugaredmap.es
//  [ 1, 2, 4, 8, 16, 32, 64, 128, 256, 512 ]