| name | oat-0-6-0 |
| description | Ultra-lightweight semantic UI component library (~8KB CSS + JS, zero dependencies) that styles HTML elements by default without classes. Provides 27 components including buttons, forms, cards, dialogs, tabs, dropdowns, toasts, tooltips, grids, and sidebar layouts with automatic light/dark mode. Use when building web applications with minimal CSS/JS footprint, semantic-first markup, no build tools, or when replacing heavier frameworks like Bootstrap or Tailwind for simple UI needs. |
OAT v0.6.0
Overview
OAT is an ultra-lightweight HTML + CSS + JS UI component library with zero dependencies. At approximately 8KB minified (CSS and JS combined), it provides most commonly needed UI components while keeping the bundle tiny.
Core philosophy: semantic-first. OAT styles HTML elements based on their semantics, not class names. A <button> is styled as a button, a <table> as a table, a <details> as an accordion — no classes required. This forces best practices and eliminates markup class pollution. Dynamic components use Web Components (<ot-tabs>, <ot-dropdown>) with minimal JavaScript built on native browser APIs (Popover API, <dialog>, <menu>).
OAT uses CSS @layer cascade layers for predictable style organization, CSS custom properties for complete theming, and light-dark() for automatic system dark mode. It supports progressive enhancement — tooltips work with native title even without JavaScript.
When to Use
- Building web applications where bundle size matters (internal tools, documentation sites, lightweight dashboards)
- Projects that prefer semantic HTML over class-heavy markup
- Replacing Bootstrap, Bulma, or other heavier CSS frameworks
- Applications needing automatic light/dark mode without extra configuration
- Prototyping or small projects without build tooling
- When you want components that work with plain HTML and minimal JS
Installation and Setup
CDN (quickest start)
<link rel="stylesheet" href="https://unpkg.com/@knadh/oat/oat.min.css">
<script src="https://unpkg.com/@knadh/oat/oat.min.js" defer></script>
Use defer on the script to ensure it runs after DOM parsing (required for tooltip enhancement and Web Component registration).
npm
npm install @knadh/oat
import '@knadh/oat/oat.min.css';
import '@knadh/oat/oat.min.js';
For selective inclusion, import individual files from @knadh/oat/css and @knadh/oat/js.
Direct download
wget https://raw.githubusercontent.com/knadh/oat/refs/heads/gh-pages/oat.min.css
wget https://raw.githubusercontent.com/knadh/oat/refs/heads/gh-pages/oat.min.js
Basic Usage
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>My App</title>
<link rel="stylesheet" href="oat.min.css">
</head>
<body>
<h1>Hello World</h1>
<p>This paragraph is styled automatically.</p>
<button>Click me</button>
<script src="oat.min.js" defer></script>
</body>
</html>
No classes needed. Headings, paragraphs, buttons, forms, tables — all styled by default.
Core Concepts
Semantic HTML Styling
OAT targets elements by their HTML tag or role, not by class:
<button> → Styled button<table> with <thead>/<tbody> → Styled data table<details>/<summary> → Accordion<dialog> → Modal dialog<progress> → Progress bar<meter> → Gauge meterrole="alert" → Alert bannerrole="switch" on checkbox → Toggle switcharia-busy="true" → Loading spinner
This means your markup is cleaner, more accessible, and works even if OAT CSS fails to load (browser defaults apply).
CSS Cascade Layers
OAT organizes styles into 5 cascade layers for predictable specificity:
@layer theme, base, components, animations, utilities;
- theme — CSS variable definitions in
:root
- base — Reset, typography, form elements
- components — Component-specific styles
- animations — Keyframes and transitions
- utilities — Helper classes
Your custom CSS (without @layer) always wins over all OAT layers.
CSS Variable Theming
Every visual property is a CSS custom property. Override in your own CSS:
:root {
--primary: #6366f1;
--radius-medium: 0.5rem;
}
See reference/03-theme-and-customization.md for the complete variable catalog (50+ variables covering colors, spacing, typography, shadows, and transitions).
Progressive Enhancement
- Tooltips work with native
title attribute even without JavaScript
- JavaScript enhances
title → styled data-tooltip via MutationObserver
- Dialog uses
commandfor/command attributes (Safari polyfill included)
- Dropdowns use native Popover API
- All animations respect
prefers-reduced-motion: reduce
Dark Mode
Automatic via color-scheme: light dark and light-dark() CSS function. Force dark mode with data-theme="dark" on <body>. Customize dark theme by scoping overrides in [data-theme="dark"] { ... }.
Component Quick Reference
Static Components (CSS only, no JS required)
| Component | Trigger | Key Attributes/Classes | Variants |
|---|
| Accordion | <details> / <summary> | name for grouping | — |
| Alert | [role="alert"] | data-variant="success|warning|error|danger" | success, warning, error, danger |
| Avatar | <figure data-variant="avatar"> | .small, .large, role="group" | small, default, large |
| Badge | .badge | .secondary, .outline, .success, .warning, .danger | secondary, outline, success, warning, danger |
| Breadcrumb | <nav> + <ol class="unstyled hstack"> | aria-current="page" | — |
| Button | <button>, <a class="button"> | data-variant="secondary|danger", .outline, .ghost | secondary, danger, outline, ghost |
| Button Sizes | — | .small, .large, .icon | small, default, large, icon |
| Button Group | <menu class="buttons"> + <li><button> | — | — |
| Card | .card (on <article>) | — | — |
| Meter | <meter> | min, max, low, high, optimum | — |
| Pagination | <nav> + <menu class="buttons"> | , , |
Dynamic Components (require oat.min.js)
| Component | Element | JS API / Events | Key Features |
|---|
| Dialog | <dialog> + commandfor/command | dialog.returnValue, close event | Focus trapping, backdrop, Escape close, Safari polyfill |
| Dropdown | <ot-dropdown> + [popover] | — | Auto-positioning, flip on overflow, keyboard nav (ArrowUp/Down/Home/End) |
| Tabs | <ot-tabs> + [role="tablist"] | activeIndex getter/setter, ot-tab-change event | ARIA management, ArrowLeft/Right nav |
| Toast | — | ot.toast(msg, title?, opts?), ot.toast.el(el, opts?), ot.toast.clear(placement?) | 6 placements, 3 variants, auto-dismiss, hover pause, custom HTML |
| Tooltip | [title] → [data-tooltip] | data-tooltip-placement="top|bottom|left|right" | 700ms delay, progressive enhancement |
Theming and Customization
Override CSS Variables
Create a custom CSS file and include it after OAT's CSS:
<link rel="stylesheet" href="oat.min.css">
<link rel="stylesheet" href="my-theme.css">
:root {
--primary: #6366f1;
--primary-foreground: #ffffff;
--radius-medium: 0.5rem;
--font-sans: 'Inter', system-ui, sans-serif;
}
Dark Mode Customization
[data-theme="dark"] {
--primary: #818cf8;
--background: #0f172a;
--card: #1e293b;
}
Selective Inclusion
For minimal bundles, include only what you need. Required base files:
00-base.css — Reset and typography01-theme.css — CSS variablesbase.js — OtBase class and polyfills
Then add component files as needed:
import '@knadh/oat/css/00-base.css';
import '@knadh/oat/css/01-theme.css';
import '@knadh/oat/css/button.css';
import '@knadh/oat/css/card.css';
import '@knadh/oat/js/base.js';
Layout and Forms
Grid System
12-column responsive grid using CSS Grid:
<div class="container">
<div class="row">
<div class="col-4">Sidebar</div>
<div class="col-8">Main content</div>
</div>
<div class="row">
<div class="col-3">A</div>
<div class="col-6">B</div>
<div class="col-3">C</div>
</div>
</div>
Classes: .container, .row, .col-{1-12}, .offset-{1-6}, .col-end. At 768px and below, columns stack to full width.
Form Elements
All form elements styled automatically. Wrap in <label data-field> for proper spacing and hint support:
<label data-field>
Email
<input type="email" placeholder="you@example.com" />
</label>
Supported inputs: text, email, password, url, date, datetime-local, file, range, checkbox, radio, select, textarea.
Input Groups
Combine inputs with fieldset.group:
<fieldset class="group">
<input type="text" placeholder="Search" />
<button>Go</button>
</fieldset>
Validation Errors
Use data-field="error" to reveal error messages:
<div data-field="error">
<label for="email">Email</label>
<input type="email" id="email" aria-invalid="true" value="bad" />
<div class="error" role="status">Invalid email address.</div>
</div>
Sidebar Layout
Responsive admin layout with sticky sidebar:
<body data-sidebar-layout>
<nav data-topnav>
<button data-sidebar-toggle class="outline">☰</button>
<span>App Name</span>
</nav>
<aside data-sidebar>
<header>Logo</header>
<nav><ul><li><a href="#">Home</a></li></ul></nav>
<footer><button class="outline">Logout</button></footer>
</aside>
<main>Page content here.</main>
</body>
Use data-sidebar-layout="always" for always-collapsible sidebar at all screen sizes. Mobile (≤768px): sidebar becomes slide-out overlay.
JavaScript API
Toast Notifications
ot.toast('Saved successfully', 'Success', { variant: 'success' });
ot.toast('Error occurred', 'Oops', { variant: 'danger', placement: 'bottom-center' });
ot.toast('Warning message', '', { variant: 'warning', duration: 6000 });
ot.toast.el(document.querySelector('#my-template'), { duration: 8000, placement: 'top-center' });
ot.toast.clear();
ot.toast.clear('top-right');
Options: variant ('success', 'danger', 'warning'), placement (6 positions, default 'top-right'), duration (ms, default 4000, 0 = persistent).
Tabs Programmatic Control
const tabs = document.querySelector('ot-tabs');
tabs.activeIndex = 2;
console.log(tabs.activeIndex);
tabs.addEventListener('ot-tab-change', (e) => {
console.log('Switched to tab:', e.detail.index);
});
Dialog Return Value
const dialog = document.querySelector('#my-dialog');
dialog.addEventListener('close', () => {
console.log(dialog.returnValue);
});
OtBase (Web Component Base Class)
All OAT Web Components extend OtBase which provides:
connectedCallback / disconnectedCallback lifecyclehandleEvent(event) — Central event handler with auto-cleanup (this.onclick, etc.)keyNav(event, idx, len, prevKey, nextKey, homeEnd) — Roving keyboard navigation helperemit(name, detail) — Fire custom events$(selector) / $$(selector) — Query helpersuid() — Unique ID generator
Recipes and Extensions
Common Patterns
- Split button:
<menu class="buttons"> + <ot-dropdown> for primary action + overflow menu
- Form card:
<article class="card"> wrapping form fields with header/footer
- Empty state: Card with
.align-center, muted text, and CTA button
- Stats dashboard: Grid of cards with badges, metrics, and progress/meter bars
See reference/08-recipes-and-patterns.md for full markup examples.
Community Extensions
- oat-chips — Chip/tag component (~1KB gzipped)
- oat-animate — Declarative animation triggers (~1KB gzipped)
Companion Libraries (same author, zero-dependency)
- tinyrouter.js (~950B) — Frontend routing
- highlighted-input.js (~450B) — Keyword highlighting in inputs
- floatype.js (~1.2KB) — Floating autocomplete
- dragmove.js (~500B) — Draggable elements
- indexed-cache.js (~2.1KB) — IndexedDB asset caching
Utility Classes
| Category | Classes |
|---|
| Flexbox | .flex, .flex-col, .items-center, .justify-center, .justify-between, .justify-end |
| Stacks | .hstack (horizontal with gap), .vstack (vertical with gap) |
| Alignment | .align-left, .align-center, .align-right |
| Text | .text-light, .text-lighter |
| Gaps | .gap-1, .gap-2, .gap-4 |
| Margins | .mt-2, .mt-4, .mt-6, .mb-2, .mb-4, .mb-6 |
| Padding | .p-4 |
| Width | .w-100 |
| Reset | .unstyled (removes list styles and link decoration) |
Advanced Topics
Getting Started: Installation methods, basic template, dark mode, selective inclusion → Getting Started
Typography and Base: Cascade layers, reset defaults, heading scale, code/blockquote/lists → Typography and Base
Theme Variables: Complete CSS variable catalog (50+ variables) with override patterns → Theme and Customization
Static Components: 14 CSS-only components (accordion, alert, avatar, badge, button, card, etc.) → Static Components
Dynamic Components: Dialog, dropdown, tabs, toast API, tooltip enhancement with full JS details → Dynamic Components
Layout and Forms: 12-column grid, form elements, input groups, validation, sidebar layout → Layout and Forms
Utilities and Helpers: Flexbox, stacks, margins, animation classes, reduced motion → Utilities and Helpers
Recipes and Extensions: Composable patterns, community extensions, companion libraries → Recipes and Patterns
Browser Support
OAT uses modern CSS features including @layer, light-dark(), color-mix(), @starting-style, nested CSS rules, and the Popover API. These require modern browsers (Chrome 120+, Firefox 128+, Safari 17.4+). The commandfor/command polyfill provides dialog support in Safari versions lacking native command API support.
