Best way to reduce length of || (or) operator?

Question

I was wondering if there's a best way to reduce comparison operator when using if else statement in JavaScript.

Suppose we have a simple function like this:

let txt = ["a","b","c","d","e","f","g","h","i","j","k","l","m","n","o","p","q","r","s","t","u","v","w","x","y","z"];

let collect_vowels = [];

txt.forEach( letter => {
    if (letter === 'a' || letter === 'e' || letter === 'i' || letter === 'o' || letter === 'u') {
        collect_vowels.push(letter);
    }
});

As you can see, we have very long || operator inside of if. I want to know if there's a better (shorter) way to write it.