some iterations on a compose function for JS

common.js

//stuff shared across many vs of compose
//util
const call = method => (...args) => obj => obj[method](...args);
let l = console.log.bind(console);

///
const compose = require(/*one of them*/);
  //fs = [x, y, z];
  //return a => x(y(z(a)));

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

//tryout
const ds = compose(double,square); //should square then double

const rev = composee(call('reverse')(),call('slice')());
const red = call('reduce');
const join = call('join');

const list = ["a","b","c","d"];

l(rev(list));
l(list);
l(join('<-')(list));
l(compose(join('<-'),rev)(list));

compose1.js

function compose(...fs){
  let last = null;
  for(let i = fs.length - 1; i >= 0; i--){
    let lastFn = last;
    let thisFn = fs[i];
    if(lastFn === null){
      last = thisFn;
    }else{
      last = x => thisFn(lastFn(x));
    }
  }
  return last;
}

compose2.js

function compose2(...fns){
  let fs = fns.reverse();
  let last = null;
  for(let i = 0; i < fs.length; i++){
    let lastFn = last;
    let thisFn = fs[i];
    if(lastFn === null){
      last = thisFn;
    }else{
      last = x => thisFn(lastFn(x));
    }
  }
  return last;
}

compose3.js

function compose3(...fs){
  return fs
    .reverse()
    .reduce(function(last, cur){
      if(last === null){
        return cur;
      }else{
        return x => cur(last(x));
      }
    },null);
}

compose4.js

function compose4(...fs){
  return fs
    .reverse()
    .reduce(function(last, cur){
      return x => cur(last(x));
    },x => x);
}

compose5.js

function compose5(...fs){
  return fs
    .reverse()
    .reduce((l,c)=> x => c(l(x)),x => x);
}

compose6.js

const comp6 = (...fs) => red((l,c)=> x => c(l(x)),x => x)(rev(fs))

recursive.js

function comp(...fs){
  //let rev, red;
//  if(fs.length === 1) return fs[0];
  let idk = red((l,c)=> x => c(l(x)),x => x);
  //can't quite get it down to 1 fn.
  return comp(idk, rev)(fs);
}