For a quiz, I am playing with Pangrams, sentences that have all 26 letters of the alphabet in them. Using Set and some RegEx it is a one-liner in JavaScript to validate them (split into two lines for readability…).

const isPangram = s => new Set(
  s.toLowerCase().replace(/[^a-z]/g, '')
).size === 26;

I've also put together a small tool for myself to write pangrams and check them whilst I type. You can see it in action here:

Do you have a shorter solution?