0xD34F

$('.button').click(function() {
  const $this = $(this);
  const $content = $this.closest('.item').find('.block');

  if ($this.hasClass('closed')) {
    $this.removeClass('closed').html('Скрыть ↑');
    $content.slideDown();
  } else {
    $this.addClass('closed').html('Показать ↓');
    $content.slideUp();
  }
}).click();

function onClick() {
  const color = `#${(Math.random() * 0xFFFFFF | 0).toString(16).padStart(6, 0)}`;
  document.querySelectorAll(`.${this.id}`).forEach(n => {
    n.style.backgroundColor = color;
  });
}

document.querySelectorAll('li').forEach(n => n.addEventListener('click', onClick));

const audio = new Audio();
const queue = [];

audio.onended = function() {
  if (queue.length) {
    audio.src = queue.shift();
    audio.play();
  }
};

function play(srcArray) {
  queue.push(...srcArray);

  if (audio.paused) {
    audio.onended();
  }
}

play([ '1.mp3', '2.mp3', '3.mp3' ]);

Вешаю на него сеттер...

function test(m) {
  let money = m;

  Object.defineProperty(this, 'money', {
    get() {
      return money;
    },
    set(val) {
      alert(`Значение свойства money меняется с ${money} на ${val}`);
      money = val;
    },
  });
}

function test(m) {
  this.money = m;

  return new Proxy(this, {
    set(target, prop, val) {
      alert(`Значение свойства ${prop} меняется с ${target[prop]} на ${val}`);
      target[prop] = val;
      return true;
    },
  });
}

const container = document.querySelector('.container');
const itemSelector = 'article';
const buttonSelector = `${itemSelector} .btn`;
const activeClass = 'active';

container.addEventListener('click', e => {
  const button = e.target.closest(buttonSelector);
  if (button) {
    button.closest(itemSelector).classList.toggle(activeClass);
  }
});

container.querySelectorAll(buttonSelector).forEach(function(n) {
  n.addEventListener('click', this);
}, e => e.currentTarget.closest(itemSelector).classList.toggle(activeClass));

const container = document.querySelector('#container');
const text = 'hello, world!!';
const delay = 300;

// можно сразу назначить таймауты для каждого из символов текста
for (const [ i, n ] of Array.prototype.entries.call(text)) {
  setTimeout(() => {
    container.insertAdjacentHTML('beforeend', `<span>${n}</span>`);
  }, 300 * i);
}

// или, назначать следующий таймаут после выполнения предыдущего
(function step(i) {
  if (i < text.length) {
    const span = document.createElement('span');
    span.textContent = text[i];
    container.insertAdjacentElement('beforeend', span);
    setTimeout(step, delay, i + 1);
  }
})(0);

// или, вместо множества таймаутов назначить один интервал
let i = 0;
const intervalId = setInterval(() => {
  const span = document.createElement('span');
  span.innerText = text[i];
  container.append(span);
  if (++i >= text.length) {
    clearInterval(intervalId);
  }
}, delay);

span {
  display: inline-block;
  animation: span .2s ease-out;
  font-size: 40px;
}
@keyframes span {
  from {
    transform: translateX(500px);
    opacity: 0;
  }
  to {
    transform: translateX(0);
    opacity: 1;
  }
}

arr.sort((a, b) => moment(b.date, 'DD.MM.YY') - moment(a.date, 'DD.MM.YY'));

const newArr = arr
  .map(n => [ n, +n.date.split('.').reverse().join('') ])
  .sort((a, b) => b[1] - a[1])
  .map(n => n[0]);

array[i+1]=true;

const ops = {
  OR: arr => arr.some(Boolean),
  AND: arr => arr.every(Boolean),
  XOR: arr => !!arr.reduce((p, c) => p ^ c, 0),
};

const logicalCalc = (arr, op) => ops[op](arr);

const ops = {
  OR(arr) {
    for (const n of arr) if (n) {
      return true;
    }
    return false;
  },
  AND(arr) {
    for (const n of arr) if (!n) {
      return false;
    }
    return true;
  },
  XOR(arr) {
    let result = 0;
    for (const n of arr) {
      result ^= n;
    }
    return !!result;
  },
};

window.name converts all stored values to their string representations using the toString method

Прежде всего мне непонятно зачем происходит сравнение с index.

$('.result').filter((i, { dataset: d }) => d.from <= id && id <= d.to)

'user.name'.split('.').reduce((obj, key) => obj[key], filter_params)

const combinations = (
  str,
  {
    charset = 'abcdefghijklmnopqrstuvwxyz',
    placeholder = '&',
  } = {}
) =>
  str.includes(placeholder)
    ? [].concat(...Array.from(
        charset,
        n => combinations(str.replace(placeholder, n), { charset, placeholder })
      ))
    : [ str ];


console.log(combinations('ih&v&'));

function combinations(
  [...str],
  {
    charset = Array.from({ length: 26 }, (_, i) => String.fromCharCode(i + 97)),
    placeholder = '&',
  } = {}
) {
  const numReplacements = str.filter(n => n === placeholder).length;
  return Array.from(
    { length: charset.length ** numReplacements },
    (_, i) => {
      let j = numReplacements;
      return str
        .map(n => n === placeholder
          ? charset[(i / (charset.length ** --j) | 0) % charset.length]
          : n)
        .join('');
    }
  );
}


console.log(combinations('#**', { charset: '0123456789ABCDEF', placeholder: '*' }));

$('body').on('click', '.myclass', function(e) {
  if (!$(e.target).hasClass('button')) {
    document.location.href = 'index.html';
  }
});

$('.button').on('click', e => e.stopPropagation());

var aNum = $(this).closest('.answers').find('.answer').length;

- change_element.attr('data-animation-in', $(this).val())
+ change_element.data('animation-in', $(this).val())

- dropdown_container.data('animation-in')
+ dropdown_container.attr('data-animation-in')

data-* attributes are used to initialize jQuery data. An element's data-* attributes are retrieved the first time the data() method is invoked upon it, and then are no longer accessed or mutated (all values are stored internally by jQuery)

$('#text').on('input', function() {
  $('#output').text(this.value.trim().replace(/\s+/g, ' ').length);
});