regex match dupe

Isogram
Isogram in JavaScript 
export function isIsogram(word) {
  return !/([a-z]).*?\1/i.test(word);
}

In the next part of the pattern .*?:

  • . looks for another character which is not a line terminator.
  • * looks for zero or more of those characters.
  • ? looks for as few of those characters as possible, until

\1 finds a repeat of the first captured character. If no repeat is found for the first captured character, then the regex tries again and matches the next a-z as the first captured character, and so on.

The i at the end of the pattern means to ignore case when matching, so [a-z] will also find [A-Z].

The ! at the beginning of the pattern is the logical NOT operator. The function returns true if the regex does not find a repeated letter.

4th Sep 2024 · Found it useful?

Other Approaches to Isogram in JavaScript

Other ways our community solved this exercise
export function isIsogram(string) {
  let word = [...string.toLowerCase()].filter(
    (letter) => letter >= "a" && letter <= "z"
  );
  return new Set(word).size == word.length;
}
filter with Set

Use filter to populate a Set. 

for (const letter of [...word]) {
  if (letter >= "a" && letter <= "z") {
    if ((letter_flags & (1 << (letter.charCodeAt(0) - A_LCASE))) != 0)
      return false;
    else letter_flags |= 1 << (letter.charCodeAt(0) - A_LCASE);
  }
  // code snipped
}
Bit field

Use a bit field to keep track of used letters.