SecretSong.js

class SecretSong {
    constructor(items) {
        this.items = items || [];
        this.lyrics = '';
        this.itemsGiven = [];
    }
    init() {
        let when = atob('T24gdGhl');
        let verb = atob('ZGF5IG9mIENocmlzdG1hcyBteSB0cnVlIGxvdmUgc2VudCB0byBtZTo=');
        const from = atob('ZG92ZXMsIGE='), to = atob('ZG92ZXMsIGFuZCBh');
        for(let i = 1;i <= this.items.length; ++i) {
            let num = i == 1 ? 'a' : i;
            this.itemsGiven.unshift(num + ' ' + this.items[i - 1]);
            let verse =
                `${when} ${this.nth(i)} ${verb} ${this.itemsGiven.join(', ')}`;
            this.lyrics += verse.replace(from, to) + '. ';
        }
    }
    nth(n) {
        let s = ['th', 'st', 'nd', 'rd'];
        return n + (s[(n - 20) % 100] || s[n] || s[0]);
    }
    sing() {
        console.log(this.lyrics);
        var msg = new SpeechSynthesisUtterance();
        msg.text = this.lyrics;
        window.speechSynthesis.speak(msg);
    }
}

const items = [
    'cGFydHJpZGdlIGluIGEgcGVhciB0cmVl',
    'dHVydGxlIGRvdmVz',
    'ZnJlbmNoIGhlbnM=',
    'Y2FsbGluZyBiaXJkcw==',
    'Z29sZCByaW5ncw==',
    'Z2Vlc2UgYS1sYXlpbmc=',
    'c3dhbnMgYS1zd2ltbWluZw==',
    'bWFpZHMgYS1taWxraW5n',
    'bGFkaWVzIERhbmNpbmc=',
    'bG9yZHMgYS1sZWFwaW5n',
    'cGlwZXJzIHBpcGluZw==',
    'ZHJ1bW1lcnMgZHJ1bW1pbmc='
];
const song = new SecretSong(items.map(atob));
song.init();
song.sing();