Alphabet class containing the english alphabet in both upper and lower casing.

alphabet.js

class Alphabet {
    constructor() {
        this.lowercaseStr = '';
        this.uppercaseStr = '';
        this.lowercaseArr = [];
        this.uppercaseArr = [];
        this.letters = this.getAlphabet();
        this._init();
    }

    _init() {
        for (const letter in this.letters) {
            if (letter === letter.toUpperCase()) {
                this.uppercaseStr += letter;
                this.uppercaseArr.push(letter);
            } else {
                this.lowercaseStr += letter;
                this.lowercaseArr.push(letter);
            }
        }
    }

    _setLetters(start, end, arr) {
        for (let i=start; i < end; i++) {
            arr[String.fromCharCode(i)] = i;
        }
    }

    getAlphabet() {
        const alphabet = [];
        this._setLetters(65, 91, alphabet);
        this._setLetters(97, 123, alphabet);
        return alphabet;
    }
}

const alphabet = new Alphabet();
console.log(alphabet);

/*
Alphabet {
  lowercaseStr: 'abcdefghijklmnopqrstuvwxyz',
  uppercaseStr: 'ABCDEFGHIJKLMNOPQRSTUVWXYZ',
  lowercaseArr:
   [ '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' ],
  uppercaseArr:
   [ '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' ],
  letters:
   [ A: 65,
     B: 66,
     C: 67,
     D: 68,
     E: 69,
     F: 70,
     G: 71,
     H: 72,
     I: 73,
     J: 74,
     K: 75,
     L: 76,
     M: 77,
     N: 78,
     O: 79,
     P: 80,
     Q: 81,
     R: 82,
     S: 83,
     T: 84,
     U: 85,
     V: 86,
     W: 87,
     X: 88,
     Y: 89,
     Z: 90,
     a: 97,
     b: 98,
     c: 99,
     d: 100,
     e: 101,
     f: 102,
     g: 103,
     h: 104,
     i: 105,
     j: 106,
     k: 107,
     l: 108,
     m: 109,
     n: 110,
     o: 111,
     p: 112,
     q: 113,
     r: 114,
     s: 115,
     t: 116,
     u: 117,
     v: 118,
     w: 119,
     x: 120,
     y: 121,
     z: 122 ] }
*/