uswds（uswds 搜索）

USWDS Development Guide

Build accessible, mobile-friendly interfaces using USWDS v3 and @trussworks/react-uswds.

Quick Reference

• Components: See references/components.md for all 47 components with React imports and CSS classes
• Design Tokens: See references/design-tokens.md for colors, spacing, typography, and all token values
• Utilities: See references/utilities.md for all utility classes organized by category
• Grid & Layout: See references/grid-layout.md for the 12-column grid system
• Sass Theming: See references/sass-theming.md for customizing USWDS via settings variables

Core Architecture

USWDS has three layers:

1. Design Tokens — Named values for color, spacing, typography (never use raw hex/px)
2. Utilities — Single-property CSS classes (bg-primary, padding-2, font-sans-lg)
3. Components — Pre-built UI patterns (usa-alert, usa-card, usa-header)

Tokens flow through functions (color('primary')), mixins (u-bg('primary')), and utility classes (.bg-primary).

React Usage (@trussworks/react-uswds)

Import components directly:

import {
  Alert, Button, Card, CardGroup, CardHeader, CardBody, CardFooter,
  Grid, GridContainer, Form, Fieldset, Label, TextInput, Select,
  Table, Tag, Tooltip, Modal, ModalToggleButton, ModalHeading, ModalFooter,
  Header, PrimaryNav, Footer, SideNav, Breadcrumb, BreadcrumbBar, BreadcrumbLink,
  StepIndicator, StepIndicatorStep, SummaryBox, SummaryBoxHeading, SummaryBoxContent,
  Search, Pagination, Accordion, GovBanner, SiteAlert, Icon,
  Checkbox, Radio, ComboBox, DatePicker, FileInput, Textarea, TimePicker,
  ButtonGroup, ProcessList, ProcessListItem, ProcessListHeading,
  Collection, CollectionItem, IconList, IconListItem,
} from '@trussworks/react-uswds';

Do NOT import USWDS JavaScript directly (import 'uswds') — it causes double-initialization of interactive components.

Key Conventions

Always Use Tokens (Never Hardcoded Values)

// WRONG
color: #005ea2;
padding: 16px;

// RIGHT
color: color('primary');
padding: units(2);

Utility Classes Follow .{property}-{token} Pattern

<div class="bg-primary text-white padding-2 margin-bottom-3 font-sans-lg">
  Content
</div>

USWDS Class Prefix: usa-

All component classes use the usa- prefix:

• .usa-alert, .usa-button, .usa-card, .usa-table
• .usa-header, .usa-footer, .usa-modal, .usa-sidenav

Responsive Prefixes

Apply at breakpoint and above (mobile-first):

<div class="grid-col-12 tablet:grid-col-6 desktop:grid-col-4">

Breakpoints: mobile-lg (480px), tablet (640px), tablet-lg (880px), desktop (1024px), widescreen (1400px)

Accessibility Requirements

USWDS enforces Section 508 / WCAG 2.1 AA:

• Color contrast: Use grade differences of 50+ for AA (see magic number system in design tokens reference)
• Semantic HTML: <nav>, <main>, <section>, <button> over <div> with roles
• ARIA attributes: aria-label on nav elements, aria-current="page" on breadcrumbs, aria-expanded on toggles
• Form accessibility: Every input needs a <Label>, use <Fieldset> + <legend> for groups, mark required fields with *
• Keyboard navigation: All interactive elements must be keyboard-accessible, trap focus in modals
• Skip navigation: Include skip-nav links before headers

Common Patterns

Page Layout

<GridContainer>
  <Grid row gap>
    <Grid col={12} tablet={{ col: 3 }}>
      <SideNav items={navItems} />
    </Grid>
    <Grid col={12} tablet={{ col: 9 }}>
      <main>{children}</main>
    </Grid>
  </Grid>
</GridContainer>

Alert

<Alert type="info" heading="Informational" headingLevel="h3">
  Body text here.
</Alert>
// type: 'info' | 'success' | 'warning' | 'error' | 'emergency'

Form with Validation

<Form onSubmit={handleSubmit}>
  <Fieldset legend="Contact Information">
    <Label htmlFor="email" requiredMarker>Email</Label>
    <TextInput id="email" name="email" type="email" validationStatus={errors.email ? 'error' : undefined} />
    {errors.email && <ErrorMessage>{errors.email}</ErrorMessage>}
  </Fieldset>
  <Button type="submit">Submit</Button>
</Form>

Modal

const modalRef = useRef<ModalRef>(null);

<ModalToggleButton modalRef={modalRef} opener>Open</ModalToggleButton>
<Modal ref={modalRef} id="my-modal" aria-labelledby="modal-heading" aria-describedby="modal-desc">
  <ModalHeading id="modal-heading">Title</ModalHeading>
  <p id="modal-desc">Description</p>
  <ModalFooter>
    <ButtonGroup>
      <ModalToggleButton modalRef={modalRef} closer>Cancel</ModalToggleButton>
      <Button type="button" onClick={handleConfirm}>Confirm</Button>
    </ButtonGroup>
  </ModalFooter>
</Modal>

Table

<Table bordered striped fullWidth>
  <thead>
    <tr>
      <th scope="col">Name</th>
      <th scope="col">Status</th>
    </tr>
  </thead>
  <tbody>
    <tr>
      <th scope="row">Item 1</th>
      <td>Active</td>
    </tr>
  </tbody>
</Table>

Card

<CardGroup>
  <Card>
    <CardHeader><h3 className="usa-card__heading">Title</h3></CardHeader>
    <CardBody><p>Content</p></CardBody>
    <CardFooter><Button>Action</Button></CardFooter>
  </Card>
</CardGroup>

Sass Configuration Entry Point

// styles.scss
@use "uswds-core" with (
  $theme-image-path: '~@uswds/uswds/dist/img',
  $theme-font-path: '~@uswds/uswds/dist/fonts',
  // Theme overrides go here
);
@forward 'uswds';
// Custom styles below

Configure theme tokens ABOVE @forward 'uswds'. See references/sass-theming.md.