text: function addTogether () {
    if (arguments.length === 1) {
      var num = arguments[0]
      if (typeof num === 'number') {
        return function (a) {
          if (typeof a === 'number') {
            return a + num
          } else {
            return undefined
          }
        }
      } else {
        return undefined
      }
    } else if (arguments.length > 1) {
      var arr = Array.from(arguments)
      for (var i = 0; i < arr.length; i++) {
        if (typeof arr[i] !== 'number') {
          break
        }
      }
      if (i === arr.length) {
        return arr.reduce(function (prev, next) {
          return prev + next
        })
      } else {
        return undefined
      }
    } else {
      return undefined
    }
  }
  
  addTogether(2, 3)
  