function sumRecur(...args) {
  if (args.length <= 2) {
    return args[0] + args[1];
  }
  return (
    args[0] +
    sumRecur(...args.slice(1))
    );
}

sumRecur(3,4,5); // 12

// Transpiled to ES5
"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); } }

function sumRecur() {
  for (var _len = arguments.length, args = Array(_len), _key = 0; _key < _len; _key++) {
    args[_key] = arguments[_key];
  }

  if (args.length <= 2) {
    return args[0] + args[1];
  }
  return args[0] + sumRecur.apply(undefined, _toConsumableArray(args.slice(1)));
}

sumRecur(3, 4, 5);



12