JS Bin// source https://jsbin.com/gajuqej

convertedCurrying.js

"use strict";

function _toConsumableArray(arr) { if (Array.isArray(arr)) { for (var i = 0, arr2 = Array(arr.length); i < arr.length; i++) arr2[i] = arr[i]; return arr2; } else { return Array.from(arr); } }

var log = console.log;

function example(a, b, c) {
  log({ a: a, b: b, c: c });
  return a * b * c;
}

var __ = Symbol("someempty string");
var isPlaceholder = function isPlaceholder(a) {
  return a === __;
};
var notPlaceholder = function notPlaceholder(a) {
  return !isPlaceholder(a);
};

var removePlaceholder = function removePlaceholder(a) {
  return a.filter(function (z) {
    return notPlaceholder(z);
  });
};

function partial(func) {
  for (var _len = arguments.length, args1 = Array(_len > 1 ? _len - 1 : 0), _key = 1; _key < _len; _key++) {
    args1[_key - 1] = arguments[_key];
  }

  var numReqArgs = func.length;

  return function _partial() {
    for (var _len2 = arguments.length, args2 = Array(_len2), _key2 = 0; _key2 < _len2; _key2++) {
      args2[_key2] = arguments[_key2];
    }

    var filledIn = args1.map(function (x) {
      return isPlaceholder(x) && args2.length ? args2.shift() : x;
    });
    var current = [].concat(_toConsumableArray(filledIn), args2);
    var validArgs = removePlaceholder(current);
    if (validArgs.length >= numReqArgs) {
      return func.apply(undefined, _toConsumableArray(validArgs));
    } else {
      return partial.apply(undefined, [func].concat(_toConsumableArray(current)));
    }
  };
}
var pa1 = partial(example, __, __, __);
var pa2 = pa1(100)(3);
pa2(3);

currying.js

"use strict";
const {log} = console;


function example(a,b,c){
  log({a,b,c});
  return a*b*c;
}

const __ = Symbol("someempty string")
const isPlaceholder = a => a===__;
const notPlaceholder = a => !(isPlaceholder(a))

const removePlaceholder = a => a.filter(z => notPlaceholder(z))

function partial(func,...args1){
  const numReqArgs = func.length;
  
  return  function _partial(...args2){
    const filledIn = args1.map(x => isPlaceholder(x) && args2.length ?
                        args2.shift() : x)
    const current = [...filledIn,...args2]
    const validArgs = removePlaceholder(current)
    if(validArgs.length>=numReqArgs){
      return func(...validArgs)
      
    }
    else{
      return partial(func,...current);
    }
  }
 
}
const pa1 = partial(example,__,__,__)
const pa2 = pa1(100)(3);
pa2(3)