0xD34F

const attrName = 'bst-click';
const elements = document.querySelectorAll(`[${attrName}]`);

const data = Array.from(
  elements,
  n => [
    n.attributes[attrName].value,
    n.classList.value,
  ]
);

const data = Array.prototype.reduce.call(
  elements,
  (acc, n) => (
    (acc[n.getAttribute(attrName)] ??= []).push(n.className),
    acc
  ),
  {}
);

hrefs.filter(n => !/\.pdf$/.test(n))
// или
hrefs.filter(n => !n.endsWith('.pdf'))
// или
hrefs.filter(n => n.split('.').pop() !== 'pdf')
// или
hrefs.filter(n => n.lastIndexOf('.pdf') !== n.length - 4)
// или
hrefs.filter(n => n.slice(-4) !== '.pdf')
// или
hrefs.filter(n => n.replace(/.*\./, '') !== 'pdf')
// или
hrefs.filter(n => n.match(/\.[^.]+$/g) != '.pdf')

const getLast = (obj, parentName) =>
  obj.next instanceof Object
    ? getLast(obj.next, obj.name)
    : { ...obj, parentName };

function getLast(obj) {
  let parentName = void 0;
  for (; obj.next; parentName = obj.name, obj = obj.next) ;
  return { ...obj, parentName };
}

нужно в 24 строки уложиться

return ''.join('0' if n == '1' else '1' for n in d)

return '1' if n == 1 else ((s := dracon(n - 1)) + '1' + invert(s)[::-1])

invert = lambda d: ''.join('0' if n == '1' else '1' for n in d)
dracon = lambda n: '1' if n == 1 else ((s := dracon(n - 1)) + '1' + invert(s)[::-1])

dr = '0' + dracon(int(input()))
print(dr)

import turtle as t
tt = t.Turtle()

for n in dr:
  if n == '1':
    tt.right(90)
    tt.forward(4)
  else:
    tt.left(90)
    tt.forward(4)

input()

const Indicator = ({ value, max = 6 }) => (
  <div>
    {Array.from({ length: max }, (_, i) => (
      <div className={`indicator-cell ${i < value ? 'active' : ''}`}></div>
    ))}
  </div>
);

.indicator-cell {
  background: white;
}
.indicator-cell.active {
  background: red;
}

<Indicator value={4} />
<Indicator value={1} />
<Indicator value={8} max={12} />

computed: {
  highlightedText() {
    const { text, search } = this;
    return search
      ? text.split(RegExp(`(${search.replace(/[\\^$|.*?+{}()[\]]/g, '\\$&')})`, 'gi'))
      : [ text ];
  },
},

<template v-for="(n, i) in highlightedText">
  <mark v-if="i % 2">{{ n }}</mark>
  <template v-else>{{ n }}</template>
</template>

code =+ code;

const count = (arr, val) => arr.filter(n => n === val).length;
// или
const count = (arr, val) => arr.reduce((acc, n) => acc + (n === val), 0);

function Counter(data, key = n => n) {
  const counted = new Map;

  for (const n of data) {
    const k = key(n);
    counted.set(k, (counted.get(k) ?? 0) + 1);
  }

  return k => counted.get(k) ?? 0;
}

const arr = [ 1, 1, NaN, 1, 2, NaN, 9, NaN, NaN, 9, 7, 'hello, world!!', 'hello, world!!' ];
const counted = Counter(arr);
console.log(counted(1)); // 3
console.log(counted(NaN)); // 4
console.log(counted('hello, world!!')); // 2
console.log(counted(10)); // 0

const counted = Counter('hello, world!!');
console.log(counted('o')); // 2
console.log(counted('l')); // 3
console.log(counted('x')); // 0

<span class="color">red</span>
<span class="color">green</span>
<span class="color">red</span>
<span class="color">red</span>

const counted = Counter(document.querySelectorAll('.color'), el => el.innerText);
console.log(counted('red')); // 3
console.log(counted('blue')); // 0

const sortedElements = [...elements].sort((a, b) =>
  +a.relations.includes(b.id) ||
  -b.relations.includes(a.id) ||
  a.name.localeCompare(b.name)
);

<a data-problem="value1">
<a data-problem="value2">

$('.problem').change(function() {
  const problems = $(':checked', this)
    .get()
    .map(({ dataset: { type, problem } }) => ({ type, problem }));

  $(this)
    .closest('.remont')
    .find('.price__item')
    .hide()
    .filter((i, { dataset: d }) =>
      problems.some(p => d.type === p.type && d.problem.includes(p.problem))
    )
    .show();
}).change();

deep:true

.product {
    display: flex;

$('.problem').change(({ target: t }) => {
  const attrsSelector = [ 'type', 'problem' ]
    .map(n => `[data-${n}="${t.dataset[n]}"]`)
    .join('');

  $(`.price-problem ${attrsSelector}`).toggle(t.checked);
}).find('input').change();

$arr3 = array_map(fn($n, $m) => array_merge($n, [ 'quantity' => $m ]), $arr1, $arr2);

$('.item img').wrap(function() {
  return '<a href="' + $(this).attr('src') + '"></a>';
});

document.querySelectorAll('.item img').forEach(n => {
  n.outerHTML = `<a href="${n.attributes.src.value}">${n.outerHTML}</a>`;
});

for (const n of document.querySelectorAll('.item img')) {
  const a = document.createElement('a');
  a.href = n.getAttribute('src');
  n.after(a);
  a.append(n);
}