Simple adding code challenge day 5

// This challenge requires you to add up all the numbers from 1 to a given argument. For example, if the parameter num is 4, your program should add up 1 + 2 + 3 + 4 and return 10. This will be pretty simple to write out as a loop. We'll maintain a variable and keep adding to it as we loop from 1 to num.

function SimpleAdding(num) {
  let sum = 0;
  for (i = 0; i <= num; i++) {
    sum = sum + i;
  }
  return sum;
}


/* More complete */
function SimpleAdding2(num) { 

  // code goes here  
  if (num < 1) return NaN;
  else if (num === 1) return 1;
  return SimpleAdding(num - 1) + num;
         
}

/* Appending */
function SimpleAdding3(num) { 

  let answer = 0;
  for (let i = 0; i <= num; i++) {
      answer += i;
  }
  return answer; 
         
}

/* Array (way overengineered) */
function SimpleAdding(num) { 

  var numbers = [];
  for(i=1;i<=num;i++){numbers.push(i);}
  var init = numbers[0] + numbers [1];
  for(i=2;i<numbers.length;i++){init = init + numbers[i];}
  return init; 
}

/* Simple */
function SimpleAdding(num) { 
  if(num === 1){
    return 1; 
  }
  return num + SimpleAdding(num - 1);
}