VibeUI

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Lazy Level

A cascader with lazy loading: the next level arrives after a delay, and skeletons of exactly the future row height stand in its place.

  • cascader
  • lazy
  • loading
  • skeleton

Preview

1440pxHost theme

Use it with AI

  1. 1. Copy the link.
  2. 2. Write to your agent in your own words and drop the link into the sentence.
  3. 3. The agent opens the link and installs the component from the registry.

put this in the header: https://vibeui.ru/c/cascader-012?lang=en

Region and city

Загружаем города

Выбрано: только регион

Show the full instructions

What the link says, spelled out. Use it when your agent cannot open links — paste this text instead.

# Install and place "cascader-012" (Lazy Level) from VibeUI

## 1. Install first — do not skip, do not recreate
Run this exact command before writing any code:
npx shadcn@latest add https://vibeui.ru/r/cascader-012.json

Registry item: https://vibeui.ru/r/cascader-012.json
Installs to: components/vibeui/cascader-012.tsx (the exact path follows this project's components.json aliases).
npm dependencies: none.
Registry dependencies: none.

Install it from the registry. Do not recreate it from the description,
do not substitute a similar component from another library, and do not
rewrite it to match the project's existing style.

## 2. What it is
A cascader with lazy loading: the next level arrives after a delay, and skeletons of exactly the future row height stand in its place.

A cascader with an async level: skeletons while the request runs, aria-busy on the list and a loading status in the header. One file, zero dependencies.

## 3. How to use it
import { Cascader012 } from "@/components/vibeui/cascader-012"

<Cascader012 heading="Region and city" delay={700} />

Read the installed file for the full prop list.

## 4. Where to place it
This is a small inline component. Put it exactly where the user asked,
inside the existing markup. Do not create a new page, section or
wrapper for it. If a similar control already sits in that spot,
replace it instead of adding a second one.

Placement: ___
(The user fills this line in. If it is still blank, ask where to put it
instead of guessing.)

## 5. Keep exactly as installed
- the local --vibeui-cascader-012-* palette — do not swap it for your theme tokens
- clearing the timer in the useEffect cleanup: without it fast switching delivers data for a branch nobody is on
- the skeleton height matching the future row — otherwise the panel jumps the moment data arrives
- aria-busy on the loading list: without it a screen reader stays silent for the whole wait
- the fixed height of both columns — the right one otherwise resizes with the number of cities
- the panel's own light surface: dark text disappears on the dark catalogue card

## 6. You may change
- the panel heading through heading
- the request duration through delay
- the tree through tree and the accent colour through accent
- the number of skeleton rows to match the expected level size

## 7. Rules
- setTimeout stands in for a request: drop in fetch and put an AbortController in the same cleanup.
- There is no error state — a real request needs a third branch with a retry button.
- Skeletons are hidden from screen readers with aria-hidden: announcing blank bars is pointless.
- Do not lift the CSS variables into globals.css: the component has to stay a single file.

## 8. Verify
- it renders with no console errors;
- it looks like the preview on the VibeUI page you copied this from;
- if it does not, you changed something listed in section 5 — put it back.

For developers

npx shadcn@latest add https://vibeui.ru/r/cascader-012.json
https://vibeui.ru/r/cascader-012.json

Компонент самодостаточен: один файл, без зависимостей, собственная палитра в локальных переменных --vibeui-cascader-012-*. Клиентский: выбранная ветка и лист живут в useState, а флаг загрузки выведен сравнением «что показано» с «что выбрано» — setState в теле эффекта не вызывается и лишнего рендера нет. Задержка эмулирует запрос через setTimeout в useEffect, таймер снимается в cleanup: без этого быстрые переключения перезаписывают друг друга и в списке оказывается ветка, которую уже никто не выбирал. Скелетон повторяет высоту будущей строки, поэтому панель не прыгает при приходе данных, а сам список помечен aria-busy — скринридер объявляет загрузку, а не молчит.

Component source

The same file your agent installs. Here in case you would rather copy it by hand.

"use client"

import { useEffect, useState } from "react"
import type { CSSProperties } from "react"

export type Cascader012Node = {
  label: string
  children: string[]
}

export type Cascader012Props = {
  heading?: string
  delay?: number
  tree?: Cascader012Node[]
  accent?: string
  className?: string
  style?: CSSProperties
}

// Идея компонента: каскад, у которого следующий уровень приходит с сервера.
// Пока запрос идёт, справа стоят скелетоны той же высоты, что и будущие
// строки, — панель не прыгает, когда данные приезжают. Уровень помечен
// aria-busy, поэтому скринридер объявляет загрузку, а не молчит. Таймер
// снимается в cleanup: без этого быстрые переключения перезаписывают друг
// друга и в списке оказывается ветка, которую уже никто не выбирал.
const STYLES = `
:where([data-vibeui-block="cascader-012"]){
--vibeui-cascader-012-bg:oklch(1 0 0);
--vibeui-cascader-012-panel:oklch(0.975 0.003 265);
--vibeui-cascader-012-fg:oklch(0.23 0.014 265);
--vibeui-cascader-012-muted:oklch(0.55 0.012 265);
--vibeui-cascader-012-border:oklch(0.9 0.006 265);
--vibeui-cascader-012-accent:oklch(0.58 0.17 35);
--vibeui-cascader-012-font:ui-sans-serif,system-ui,-apple-system,"Segoe UI",Roboto,"Helvetica Neue",Arial,sans-serif;
}
[data-vibeui-block="cascader-012"]{
display:flex;flex-direction:column;gap:0.625rem;
width:100%;max-width:25rem;box-sizing:border-box;padding:0.875rem;
background:var(--vibeui-cascader-012-bg);color:var(--vibeui-cascader-012-fg);
border:1px solid var(--vibeui-cascader-012-border);border-radius:1rem;
font-family:var(--vibeui-cascader-012-font);
box-shadow:0 18px 40px -32px oklch(0.2 0.03 265 / 55%);
}
[data-vibeui-block="cascader-012"] *{box-sizing:border-box}
[data-vibeui-block="cascader-012"] [data-part="head"]{
display:flex;align-items:baseline;justify-content:space-between;gap:0.5rem;
}
[data-vibeui-block="cascader-012"] [data-part="heading"]{
margin:0;font-size:0.8125rem;font-weight:650;letter-spacing:-0.01em;
}
[data-vibeui-block="cascader-012"] [data-part="status"]{
display:inline-flex;align-items:center;gap:0.3125rem;
font-size:0.6875rem;color:var(--vibeui-cascader-012-muted);
}
[data-vibeui-block="cascader-012"] [data-part="spinner"]{
width:0.625rem;height:0.625rem;border-radius:50%;
border:1.5px solid color-mix(in oklab,var(--vibeui-cascader-012-accent) 30%,transparent);
border-top-color:var(--vibeui-cascader-012-accent);
animation:vibeui-cascader-012-spin .7s linear infinite;
}
@keyframes vibeui-cascader-012-spin{to{transform:rotate(360deg)}}
[data-vibeui-block="cascader-012"] [data-part="grid"]{
display:grid;grid-template-columns:minmax(0,1fr) minmax(0,1.15fr);gap:0.375rem;
}
[data-vibeui-block="cascader-012"] [data-part="pane"]{
display:flex;flex-direction:column;gap:0.125rem;margin:0;padding:0.25rem;
list-style:none;height:10.5rem;overflow:auto;overscroll-behavior:contain;
background:var(--vibeui-cascader-012-panel);
border:1px solid var(--vibeui-cascader-012-border);border-radius:0.75rem;
}
[data-vibeui-block="cascader-012"] [data-part="option"]{
display:flex;align-items:center;gap:0.375rem;width:100%;
padding:0.375rem 0.5rem;border:0;border-radius:0.5rem;
background:transparent;color:inherit;font:inherit;font-size:0.8125rem;
text-align:left;cursor:pointer;
transition:background-color .14s ease,color .14s ease;
}
[data-vibeui-block="cascader-012"] [data-part="option"] span{
flex:1 1 auto;min-width:0;overflow:hidden;text-overflow:ellipsis;white-space:nowrap;
}
[data-vibeui-block="cascader-012"] [data-part="option"]:hover{
background:color-mix(in oklab,var(--vibeui-cascader-012-accent) 10%,transparent);
}
[data-vibeui-block="cascader-012"] [data-part="option"]:focus-visible{
outline:2px solid var(--vibeui-cascader-012-accent);outline-offset:-2px;
}
[data-vibeui-block="cascader-012"] [data-part="option"][aria-current="true"]{
background:color-mix(in oklab,var(--vibeui-cascader-012-accent) 16%,transparent);
color:var(--vibeui-cascader-012-accent);font-weight:600;
}
[data-vibeui-block="cascader-012"] [data-part="arrow"]{
flex:0 0 auto;width:0.3125rem;height:0.3125rem;
border-right:1.5px solid currentColor;border-top:1.5px solid currentColor;
transform:rotate(45deg);opacity:.5;
}
/* Скелетон повторяет высоту будущей строки, иначе панель дёргается. */
[data-vibeui-block="cascader-012"] [data-part="skeleton"]{
height:1.625rem;margin:0 0.0625rem;border-radius:0.5rem;
background:linear-gradient(90deg,
oklch(0.93 0.006 265) 0%,
oklch(0.97 0.004 265) 50%,
oklch(0.93 0.006 265) 100%);
background-size:200% 100%;
animation:vibeui-cascader-012-shimmer 1.1s ease-in-out infinite;
}
@keyframes vibeui-cascader-012-shimmer{
from{background-position:200% 0}
to{background-position:-40% 0}
}
[data-vibeui-block="cascader-012"] [data-part="footer"]{
margin:0;padding-top:0.5rem;border-top:1px solid var(--vibeui-cascader-012-border);
font-size:0.75rem;color:var(--vibeui-cascader-012-muted);
}
[data-vibeui-block="cascader-012"] [data-part="footer"] b{
color:var(--vibeui-cascader-012-fg);font-weight:650;
}
@media (prefers-reduced-motion:reduce){
[data-vibeui-block="cascader-012"] *{animation:none!important;transition:none!important}
}
`

const DEFAULT_TREE: Cascader012Node[] = [
  {
    label: "Северо-Запад",
    children: ["Санкт-Петербург", "Псков", "Великий Новгород", "Мурманск"],
  },
  {
    label: "Центр",
    children: ["Москва", "Тула", "Ярославль", "Калуга", "Рязань"],
  },
  {
    label: "Урал",
    children: ["Екатеринбург", "Челябинск", "Пермь"],
  },
  {
    label: "Сибирь",
    children: ["Новосибирск", "Красноярск", "Томск", "Иркутск"],
  },
]

/**
 * Каскад с ленивой подгрузкой уровня: скелетоны на время запроса и aria-busy.
 * Один файл, ноль зависимостей, собственная палитра.
 */
export function Cascader012({
  heading = "Регион и город",
  delay = 700,
  tree = DEFAULT_TREE,
  accent,
  className,
  style,
}: Cascader012Props) {
  const [branch, setBranch] = useState(0)
  const [leaf, setLeaf] = useState<string | null>(null)
  // Загрузка выведена из состояния, а не выставлена в эффекте: сравнение
  // «что показано» с «что выбрано» переключает скелетоны без лишнего рендера.
  const [ready, setReady] = useState<number | null>(null)
  const loading = ready !== branch

  useEffect(() => {
    const timer = setTimeout(() => setReady(branch), delay)

    return () => clearTimeout(timer)
  }, [branch, delay])

  const children = tree[branch]?.children ?? []

  const palette = {
    ...(accent ? { "--vibeui-cascader-012-accent": accent } : null),
    ...style,
  } as CSSProperties

  return (
    <>
      <style href="vibeui-cascader-012" precedence="medium">
        {STYLES}
      </style>
      <div
        data-vibeui-block="cascader-012"
        className={className}
        style={palette}
      >
        <div data-part="head">
          <p data-part="heading">{heading}</p>
          <span data-part="status" aria-live="polite">
            {loading ? (
              <>
                <i data-part="spinner" aria-hidden="true" />
                Загружаем города
              </>
            ) : (
              `${children.length} городов`
            )}
          </span>
        </div>
        <div data-part="grid">
          <ul data-part="pane" aria-label="Регион">
            {tree.map((node, index) => (
              <li key={node.label}>
                <button
                  data-part="option"
                  type="button"
                  aria-current={index === branch ? "true" : undefined}
                  onClick={() => {
                    setBranch(index)
                    setLeaf(null)
                  }}
                >
                  <span>{node.label}</span>
                  <i data-part="arrow" aria-hidden="true" />
                </button>
              </li>
            ))}
          </ul>
          <ul data-part="pane" aria-label="Город" aria-busy={loading}>
            {loading
              ? [0, 1, 2, 3].map((row) => (
                  <li key={row} data-part="skeleton" aria-hidden="true" />
                ))
              : children.map((city) => (
                  <li key={city}>
                    <button
                      data-part="option"
                      type="button"
                      aria-current={leaf === city ? "true" : undefined}
                      onClick={() => setLeaf(city)}
                    >
                      <span>{city}</span>
                    </button>
                  </li>
                ))}
          </ul>
        </div>
        <p data-part="footer" aria-live="polite">
          Выбрано:{" "}
          <b>{leaf ? `${tree[branch].label} → ${leaf}` : "только регион"}</b>
        </p>
      </div>
    </>
  )
}