Сергей Соколов

// вместо
    price = price.filter(
      (i) => i.id !== id
    );

// попробуйте
  const priceIndex = price.findIndex(({ id: priceId }) => priceId === id);
  if (priceIndex > -1) price.splice(priceIndex, 1);

pet_1 = { name: "Шарик", age: 10 };
pet_2 = { name: "Жучка", age: 5 };

function getName() {
  return [this.name, this.age].join(' ');
}

pet_1.getName = getName;
pet_2.getName = getName;

pet_1.getName(); // Шарик 10
pet_2.getName(); // Жучка 5

pet_1 = { name: "Шарик", age: 10 };
pet_2 = { name: "Жучка", age: 5 };

function getName() {
  return [this.name, this.age].join(' ');
}

const mixin = { getName };

Object.assign(pet_1, mixin);
Object.assign(pet_2, mixin);

pet_1.getName(); // Шарик 10
pet_2.getName(); // Жучка 5

const zip = (arr1, arr2) => arr1.reduce(
  (acc, head, i) => (acc.push({ ...arr2[i], head }), acc),
  []
);

zip(mass1, mass2) 
/* [
  { t1: "aa", p1: "lot", head: "zn1" },
  { t1: "ab", p1: "kot", head: "zn2" },
  { t1: "ac", p1: "mot", head: "zn3" },
] */

window.isLoaded = false;
window.addEventListener('load', () => {
  window.isLoaded = true;
});

window.isQueued = false; // уже ждём в очереди?
function nowOrLater() {
  if (!window.isLoaded) {
    if (!window.isQueued) {
      window.addEventListener('load', nowOrLater);
      window.isQueued = true;
    }
    return;
  }
 
  // тут код котовый выполнить только после 
}

const Main = styled.main`
  background-color: black;
  height: 100vh;
`

function App(props) {
  const { message } = props;
  return (
    <Main>
      <div className="App">
        {message}
      </div>
    </Main>
  );
}

- if (walk.length > 10 || walk.length < 10) return false;
+ if (walk.length !== 10) return false;

const isValidWalk = walk => {
  if (walk.length !== 10) return false;
  const counts = walk.reduce((acc, c) => (acc[c]++, acc), { w: 0, n: 0, e: 0, s: 0 });
  return counts.e === counts.w && counts.n === counts.s;
};

const randomArr = () => {
  // ...

  return arr;
};

const randomArr = () => Array.from({length: 10}, () => (Math.random() * 10) | 0);
// [ 0, 3, 2, 4, 2, 1, 1, 5, 2, 5 ]

const randomArr = () => {
  const arr = Array.from({length: 10}, (_, i) => i + 1); // [1, 2, .. 10]
  for (let i = 0; i < 10; i++) {
    const j = i + Math.floor(Math.random() * (10 - i));
    [arr[i], arr[j]] = [arr[j], arr[i]]; // местами поменять
  }
  return arr;
}
// [ 6, 7, 9, 3, 1, 8, 10, 2, 4, 5 ]

- let input = document.getElementsByClassName('form-control');
+ const input = document.querySelector('input.form-control');

letterElement.startsWith('A')

'Andrew'.startsWith('A') // true
'Dmitriy'.startsWith('A') // false

const arrBig = [
  { _id: 1, one: 7, two: 5 },
  { _id: 2, one: 6, two: 3 },
  { _id: 3, one: 4, two: 7 },
  { _id: 4, one: 15, two: 2 },
];

const arrSmall = [{ _id: 1, next: 22, gen: 54 }, { _id: 3, next: 6, gen: 3 }];

const key = '_id';
const dictSmall = arrSmall.reduce((acc, c) => {
  acc[c[key]] = c;
  return acc;
}, {});

const template = { next: 0, gen: 0 };
const addKeys = Object.keys(template);

const result = arrBig.map(item => {
  const nuItem = { ...item, ...template };
  const addendum = dictSmall[item[key]];
  if (addendum) {
    addKeys.forEach(key => (nuItem[key] = addendum[key]));
  }
  return nuItem;
});
/* [
  {"_id":1,"one":7,"two":5,"next":22,"gen":54},
  {"_id":2,"one":6,"two":3,"next":0,"gen":0},
  {"_id":3,"one":4,"two":7,"next":6,"gen":3},
  {"_id":4,"one":15,"two":2,"next":0,"gen":0}
] */

const makeDate = HHMM => {
  const [H, M] = HHMM.split(':').map(Number);
  const D = new Date();
  D.setHours(H);
  D.setMinutes(M);
  D.setSeconds(0);
  return D;
};

const oo = n => n.toString().padStart(2, '0'); // 5 => '05'

const fillTime = (startHHMM, finishHHMM, intervalMinutes) => {
  let startDate = makeDate(startHHMM);
  let finishDate = makeDate(finishHHMM);
  if (startDate > finishDate) { // объекты Date можно так сравнивать
    [startDate, finishDate] = [finishDate, startDate]; // поменять местами
  }

  const dates = [];
  const D = new Date(startDate);
  while (D <= finishDate) {
    dates.push(new Date(D));
    D.setMinutes(D.getMinutes() + intervalMinutes);
  }

  return dates.map(D => [D.getHours(), D.getMinutes()].map(oo).join(':'));
};

console.log(fillTime('15:56', '18:15', 17));
// [ "15:56", "16:13", "16:30", "16:47", "17:04", "17:21", "17:38", "17:55", "18:12" ]

const N = 3;

const delay = ms => new Promise(res => setTimeout(res, ms));

const next = () => {
  if (items.length > 0) {
    return download(items.shift())
      .then(delay(500 + Math.floor(Math.random() * 500))) // случайная пауза между закачками
      .then(next);
  }
};

const works = Array.from({ length: N }, () =>
  Promise.resolve()
    .then(next)
    .catch(console.error)
);

Promise.all(works).then(() => console.log('All Done'));