text: /*
  Description:
  It involves implementing a program that sums the digits of a non-negative integer. For example, the sum of 3433 digits is 13.
  
  Digits can be a number or a string, and you should control it is no undefined and return an empty string.
  
  To give you a little more excitement, the program will not only write the result of the sum, but also write all the sums used: 3 + 4 + 3 + 3 = 13.
  */
  function sum(digits) {
   if (digits===0) return '0 = 0'
   if (!digits) return ''
   digits=digits+''
   return `${digits.split``.join(' + ')} = ${digits.split(``).reduce((a,b)=>a+b*1,0)}`
  }
  