0xD34F

data: () => ({
  numShow: 0,
  ...

computed: {
  itemsToShow() {
    return this.items.slice(0, this.numShow);
  },
  ...

methods: {
  showNext() {
    this.numShow = Math.min(this.items.length, this.numShow + 1);
  },
  hidePrev() {
    this.numShow = Math.max(0, this.numShow - 1);
  },
  ...

<transition-group
  @after-enter="showNext"
  @after-leave="hidePrev"
  ...
>
  <div 
    v-for="(n, i) in itemsToShow"
    :key="n.id"
    ...
  >
  ...

methods: {
  run() {
    this.numShow += ({
      0: 1,
      [this.items.length]: -1,
    })[this.numShow] || 0;
  },
  ...

data: () => ({
  types: [
    { id: null, name: 'Все' },
    { id: ..., name: '...' },
    { id: ..., name: '...' },
    ...
  ],
  active: null,
  ...

<button v-for="n in types" @click="active = n.id">{{ n.name }}</button>

<!-- или -->

<select v-model="active">
  <option v-for="n in types" :value="n.id">{{ n.name }}</option>
</select>

<!-- или -->

<label v-for="n in types">
  <input type="radio" name="type" :value="n.id" v-model="active">
  {{ n.name }}
</label>

computed: {
  filteredItems() {
    const { items, active } = this;
    return active ? items.filter(n => n.type === active) : items;
  },
  ...

<tr v-for="(n, i) in filteredItems">
  ...

ALTER TABLE "table_name" ALTER COLUMN "column_name" SET DEFAULT '';

const positives = arr.filter(n => n > 0);
const minPositive = positives.length
  ? Math.min(...positives)
  : null;

const minPositive = arr.reduce((min, n) => (n > 0 && (n < min || min === null)) ? n : min, null);

const classes = $buttons.get().map(n => n.dataset.set);

$buttons.click(function() {
  $('.current').removeClass('current');
  $(this).addClass('current');

  $blocks.removeClass(classes.join(' ')).addClass(this.dataset.set);
});

let currentClass = null;

$buttons.click(function() {
  $('.current').removeClass('current');
  $(this).addClass('current');

  const newClass = this.dataset.set;
  $blocks.removeClass(currentClass).addClass(newClass);
  currentClass = newClass;
});

const parent = document.querySelector('здесь селектор элемента с абзацами');
const el = document.querySelector('а здесь - элемента, который хотите перенести');

const last = parent.lastElementChild;

// или

const last = parent.querySelector(':scope > :last-child');

// или

const last = parent.children[parent.children.length - 1];

// или

const [ last ] = Array.prototype.slice.call(parent.children, -1);

last.before(el);

// или

last.insertAdjacentElement('beforebegin', el);

// или

last.replaceWith(el, last);

// или

parent.insertBefore(el, last);

class App extends React.Component {
  state = {
    data: [
      '#088A85', '#0B2F3A', '#0B0B3B', '#2A0A29', '#B4045F',
      '#FA58F4', '#A9BCF5', '#58FA82', '#A9F5F2', '#CED8F6',
    ].map((n, i) => ({
      id: i + 1,
      color: n,
      title: `block #${i}`,
      opened: false,
    })),
  }

  updateItem(index, key, val) {
    const data = [...this.state.data];
    data[index][key] = val;
    this.setState({ data });
  }

  render() {
    return (
      <div>{this.state.data.map(({ id, color, title, opened }, i) => (
        <div key={id}>
          <div
            className="square"
            style={{ backgroundColor: color }}
            onClick={() => this.updateItem(i, 'opened', !opened)}
          >
            <p>{title}</p>
          </div>
          {opened &&
          <div>
            <input
              value={color}
              onChange={e => this.updateItem(i, 'color', e.target.value)}
            />
            <input
              value={title}
              onChange={e => this.updateItem(i, 'title', e.target.value)}
            />
          </div>}
        </div>))}
      </div>
    )
  }
}

.square {
  width: 100px;
  height: 100px;
}

.closest('.services_button_block').find('.services_nomer')

$('.services_minus').click(function() {
  $(this)
    .closest('.services_button_block')
    .find('.services_nomer')
    .text((i, text) => Math.max(0, text - 1));
});

$('.services_plus').click(function() {
  $(this)
    .closest('.services_button_block')
    .find('.services_nomer')
    .text((i, text) => +text + 1);
});

почему после возвращения из рекурсивного вызова i=3 а не 2?

if (numbers[i].length) {

function flat(arr) {
  const result = [];

  for (const n of arr) {
    if (n instanceof Array) {
      result.push(...flat(n));
    } else {
      result.push(n);
    }
  }

  return result;
}

// или

const flat = arr =>
  Array.prototype.concat.apply(
    [],
    arr.map(n => Array.isArray(n) ? flat(n) : n)
  );

const interval = 5 * 60 * 1000 // 5 минут, ага
const x = moment(Math.ceil(moment() / interval) * interval).format('HH:mm:ss')

Почему я не могу сделать просто func(args) ?

Зачем нужно подставлять контекст?

$elems.change(function() {
  ...
}).change();

function onChange() {
  ...
}

$elems.change(onChange).each(onChange);

class Game extends React.Component {
  state = {
    panesCurrent: [],
    panesDefault: [ 1, 1, 1, 0, -1, -1, -1 ],
    panesWin: [ -1, -1, -1, 0, 1, 1, 1 ],
  }

  componentDidMount() {
    this.reset();
  }

  componentDidUpdate() {
    if (this.state.panesCurrent.every((n, i) => n === this.state.panesWin[i])) {
      setTimeout(alert, 25, 'WIN');
    }
  }

  onClick(index) {
    const clicked = this.state.panesCurrent[index];
    if (clicked === 0) {
      return;
    }

    for (let i = 1; i <= 2; i++) {
      const t = index + clicked * i;
      if (this.state.panesCurrent[t] === 0) {
        const panes = [...this.state.panesCurrent];
        [ panes[index], panes[t] ] = [ panes[t], panes[index] ];
        this.setState({ panesCurrent: panes });
        break;
      }
    }
  }

  reset = () => {
    this.setState(({ panesDefault }) => ({
      panesCurrent: [...panesDefault],
    }));
  }

  render() {
    return (
      <div>
        <button onClick={this.reset}>reset</button>
        <div className="game">
          {this.state.panesCurrent.map((n, i) => (
            <div
              className={'pane ' + [ 'left', '', 'right' ][n + 1]}
              onClick={() => this.onClick(i)}
            ></div>
          ))}
        </div>
      </div>
    )
  }
}

.game {
  font-size: 5px;
}

.pane {
  display: inline-block;
  width: 10em;
  height: 10em;
  margin: 1em;
}

.pane.right::after,
.pane.left::after {
  position: relative;
  display: inline-flex;
  justify-content: center;
  align-items: center;
  width: 100%;
  height: 100%;
  font-family: monospace;
  font-size: 4em;
}
.pane.right::after {
  content: "-->";
  color: red;
  border: 2px solid red;
}
.pane.left::after {
  content: "<--";
  color: lime;
  border: 2px solid lime;
}