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.
- isIsogram("isogram") should return true.
- isIsogram("") should return true.
- isIsogram("moOse") should return false.
function isIsogram(str) {
// your code here
}