Антон Горецкий

<select name="nm" id="nam">
  <option value="QBC">QBC</option>
  <option value="QEF">QEF</option>
  <option value="GHI" selected>GHI</option> <!-- этот вариант будет выбран-->
  <option value="KLM">KLM</option>
</select>

import React, { useState, useEffect } from 'react'

const LocalStorage = () => {
  const date = [
    { symbol: 'RU', label: 'рубль' },
    { symbol: 'USD', label: 'доллар' },
    { symbol: 'EUR', label: 'евро' }
  ]

  const [curr, setCurrencies] = useState(date)
  const [currentSymbol, setCurrentSymbol] = useState("EUR") // опция выбранная по умолчанию (если нет данных в localstorage)

// срабатывает один раз при загрузке компонента
  useEffect(() => {
    if(localStorage.getItem('symbol')) {
      const item = localStorage.getItem('symbol')
      setCurrentSymbol(item)
    }
  }, [])

// обработчик - срабатывает при выборе опции списка
  const selectHandler = (e) => {
    localStorage.setItem('symbol', e.target.value)
    setCurrentSymbol(e.target.value)
  }

  return (
    <div>
      <select onChange={selectHandler} value={currentSymbol}>
        {
          curr.map(currencies => (
            <option key={currencies.symbol} value={currencies.symbol}>
              {currencies.symbol} {currencies.label}
            </option>
          )
          )
        }
      </select>
    </div>
  )
}

export default LocalStorage

import React, { Component } from 'react'


class ClassLocal extends Component {
  constructor(props){
    super(props);
    this.state = {
      curr: [
        { symbol: "RU", label: "рубль" },
        { symbol: "USD", label: "доллар" },
        { symbol: "EUR", label: "евро" }
      ],
      currentSymbol: "EUR"
    }
  }


  componentDidMount() {
    if(localStorage.getItem('symbol')) {
      const item = localStorage.getItem('symbol');
      this.setState({currentSymbol: item})
    }
  }


  selectHandler = (e) => {
    localStorage.setItem('symbol', e.target.value)
    this.setState({currentSymbol: e.target.value})
  }

  render() {
    return (
      <div>
        <select onChange={this.selectHandler} value={this.state.currentSymbol}>
          {
            this.state.curr.map(currencies => (
                <option key={currencies.symbol} value={currencies.symbol}>
                  {currencies.symbol} {currencies.label}
                </option>
              )
            )
          }
        </select>
      </div>
    )
  }
}

export default ClassLocal

input.addEventListener("keydown", (e) => {
    if (
      e.ctrlKey ||
      e.altKey ||
      e.shiftKey ||
      e.keyCode == 9 ||
      e.keyCode == 20
    ) {
      return false;
    }
}

function preparedData<T extends Record<string, {name: string, id: string}[]>>(data: T) {
  return Object.keys(data).map((key) => {
    return data[key as keyof T].map((a) => ({
      val: a.name,
      newId: a.id,
    }));
  });
}

function rgbaToAndroid1(rgba) {
  const c = new Uint8Array([
    rgba[2],
    rgba[1],
    rgba[0],
    Math.round(rgba[3] * 255)
  ]);
  return new Uint32Array(c.buffer)[0];
}

// либо
function rgbaToAndroid2(rgba) {
  let color = 0;
  for (let i = 0; i < 3; i++) {
    color += rgba[i] * 2 ** ((2 - i) * 8);
  }

  color += Math.round(rgba[3] * 255) * 2 ** (3 * 8);
  return color;
}

console.log(rgbaToAndroid1([255, 122, 107, 1]));
console.log(rgbaToAndroid2([255, 122, 107, 1]));

let checked = null;

$('input').click(function() {
  checked = checked === this.value ? null : this.value;
  this.checked = !!checked;
});

// или

document.querySelectorAll('input').forEach(function(n) {
  n.addEventListener('click', this);
}, function({ target: t }) {
  t.checked = !!(this[0] = this[0] === t ? null : t);
}.bind([]));

const $checkboxes = $('input').change(function() {
  if (this.checked) {
    $checkboxes.not(this).prop('checked', false);
  }
});

// или

const checkboxes = document.querySelectorAll('input');
const onChange = e => checkboxes.forEach(n => n.checked &&= n === e.target);
checkboxes.forEach(n => n.addEventListener('change', onChange));

function Validation(arr) {
  return arr.filter((el) => {
    return typeof el.age === "number"
      && el.full_name !== undefined
      && el.full_name.charAt(0) === el.full_name.charAt(0).toUpperCase()
      && el.gender !== undefined
      && el.gender.charAt(0) === el.gender.charAt(0).toUpperCase()
      && el.note !== undefined
      && el.note.charAt(0) === el.note.charAt(0).toUpperCase()
      && el.state !== undefined
      && el.state.charAt(0) === el.state.charAt(0).toUpperCase()
      && el.city !== undefined
      && el.city.charAt(0) === el.city.charAt(0).toUpperCase()
      && el.country !== undefined
      && el.country.charAt(0) === el.country.charAt(0).toUpperCase()
}

function firstLetterIsUpper(str) {
  return typeof(str) === 'string'
    && str.length
    && str.charAt(0) === str.charAt(0).toUpperCase()
}
function Validation(arr) {
  return arr.filter((el) => {
    return typeof el.age === "number"
      && firstLetterIsUpper(el?.full_name)
      && firstLetterIsUpper(el?.gender)
      && firstLetterIsUpper(el?.note)
      && firstLetterIsUpper(el?.state)
      && firstLetterIsUpper(el?.city)
      && firstLetterIsUpper(el?.country)
}