Output:
a
a b
a b c
a b c d
a b c d e

var pyramid = function(maxNum) {
	var alphabetArr = ['a', 'b', 'c', 'd', 'e'];
  for(var i=1; i<=maxNum; i++) {
    var newArr = new Array();
    for(var j=1; j<=i; j++) {
       newArr.push(alphabetArr[j-1]);
    }
    console.log(newArr.join(" ") + "\n");
  }
}
pyramid(5);