Extends the previous curry.js to allow syntax with holes eg: fn("a", _, "c")("b")

curry-with-holes.js

function toArray(args) {
  return [].slice.call(args);
}
 
function sub_curry(fn /*, variable number of args */) {
  var args = [].slice.call(arguments, 1);
  return function () {
    return fn.apply(this, args.concat(toArray(arguments)));
  };
}
 
function curry (fn, length, args, holes) {
  length = length || fn.length;
  args = args || [];
  holes = holes || [];
  return function() {
    var _args = args.slice(0),
        _holes = holes.slice(0),
        argStart = _args.length,
        holeStart = _holes.length,
        arg, i;
    for(i = 0; i < arguments.length; i++) {
      arg = arguments[i];
      if(arg === _ && holeStart) {
        holeStart--;
        _holes.push(_holes.shift()); // move hole from beginning to end
      } else if (arg === _) {
        _holes.push(argStart + i); // the position of the hole.
      } else if (holeStart) {
        holeStart--;
        _args.splice(_holes.shift(), 0, arg); // insert arg at index of hole
      } else {
        _args.push(arg);
      }
    }
    if(_args.length < length) {
        return curry.call(this, fn, length, _args, _holes);
    } else {
        return fn.apply(this, _args);
    }
  }
}
 
var f = curry(function(a, b, c) { return [a, b, c]; });
var g = curry(function(a, b, c, d, e) { return [a, b, c, d, e]; });

// all of these are equivalent
f("a","b","c");
f("a")("b")("c");
f("a", "b", "c");
f("a", _, "c")("b");
f( _, "b")("a", "c");
//=> ["a", "b", "c"]

// all of these are equivalent
g(1, 2, 3, 4, 5);
g(_, 2, 3, 4, 5)(1);
g(1, _, 3)(_, 4)(2)(5);
//=> [1, 2, 3, 4, 5]