Redusing arguments

to-curry-any.js

const curry = (fn, ...initialArgs) => {
  let value;
  const fnx = (...curryArgs) => {
    value = fn.apply(null, initialArgs.concat(curryArgs));
    return fnx;
  }

  Object.defineProperty(fnx, 'valueOf', {value: () => value});

  return fnx;
}

to-curry.js

const curry = (fn, ...initialArgs) => {
  let value;
  const fnx = (...curryArgs) => {
    if(initialArgs.length || curryArgs.length) {    
      value = initialArgs.concat(curryArgs).reduce(fn);
    }
    return fnx;
  }

  Object.defineProperty(fnx, 'valueOf', {value: () => value});

  return fnx();
}