0xD34F

toInsert = 'test.'
newStr = str.dup.sub!(/(?<=www\.)/, toInsert) || (toInsert + str)

const result = arr.flat().map((n, i) => ({ ...n, id: -~i }));

const result = [];

for (const n of arr) {
  for (const m of n) {
    result.push({
      ...m,
      id: result.length + 1,
    });
  }
}

const coord = [ 0, 0 ];
const step = 10;

const moveFunc = e => {
  const shift = ({
    ArrowUp: [ 0, -1 ],
    ArrowDown: [ 0, 1 ],
    ArrowLeft: [ -1, 0 ],
    ArrowRight: [ 1, 0 ],
  })[e.code];

  if (shift) {
    div.style.left = `${coord[0] += shift[0] * step}px`;
    div.style.top = `${coord[1] += shift[1] * step}px`;
  }
};

const result = Array.from(
  document.querySelectorAll('#spisok > div > p > br'),
  n => n.nextSibling.textContent.trim()
);

const result = Array.prototype.map.call(
  document.getElementById('spisok').getElementsByTagName('button'),
  n => n.previousSibling.nodeValue.replace(/(^\s+)|(\s+$)/g, '')
);

const makeOrderList = str =>
  Object.fromEntries(Array.from(
    str.matchAll(/(\d+) ([^,]+)/g),
    n => [ n[2].replace(/ /g, '_'), +n[1] ]
  ));

const makeOrderList = str => str
  .split(', ')
  .map(n => [ n.split(' ').slice(1).join('_'), parseInt(n) ])
  .filter(n => !Number.isNaN(n[1]))
  .reduce((acc, n) => (acc[n[0]] = n[1], acc), {});

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')

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

<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