How to generate an array of alphabet in jQuery?

A short ES6 version:

const alphabet = [...'abcdefghijklmnopqrstuvwxyz'];
console.log(alphabet);

Personally I think the best is:

alphabet = 'abcdefghijklmnopqrstuvwxyz'.split('');

Concise, effective, legible, and simple!

EDIT: I have decided, that since my answer is receiving a fair amount of attention to add the functionality to choose specific ranges of letters.

function to_a(c1 = 'a', c2 = 'z') {
    a = 'abcdefghijklmnopqrstuvwxyz'.split('');
    return (a.slice(a.indexOf(c1), a.indexOf(c2) + 1)); 
}

console.log(to_a('b', 'h'));

In case anyone came here looking for something they can hard-code, here you go:

["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"]

You can easily make a function to do this for you if you'll need it a lot

function genCharArray(charA, charZ) {
    var a = [], i = charA.charCodeAt(0), j = charZ.charCodeAt(0);
    for (; i <= j; ++i) {
        a.push(String.fromCharCode(i));
    }
    return a;
}
console.log(genCharArray('a', 'z')); // ["a", ..., "z"]