Isograms

• An isogram is a word that has no repeating letters, consecutive or non-consecutive.
• Implement a function that determines whether a string that contains only letters is an isogram.
• Assume the empty string is an isogram. Ignore letter case.

Example

• "Dermatoglyphics" --> true
• "aba" --> false
• "moOse" --> false (ignore letter case)

Note : An empty string is also an isogram

Challenges (0/3 done)

• isIsogram("isogram") should return true
• isIsogram("") should return true
• isIsogram("moOse") should return false

function isIsogram(str) {
  // your code here
}