refactor: extract withProps mixin to eliminate TypedBase/observedAttributes boilerplate

18 components now use withProps(HTMLElement, PROPS) instead of
repeating TypedBase cast, static get observedAttributes(), and
static { definePropAccessors(...) } in each file.

Adds src/core/with-props.ts — a mixin factory that derives
PropTypesFromTable, defines property accessors, and sets up
observedAttributes from a PROPS table in a single expression.

src/components/leaflet-circle-marker.ts

@@ -1,5 +1,6 @@
 import { CircleMarker } from 'leaflet';
-import { registerWithParent, buildOptions, definePropAccessors } from '../core/utils.js';
+import { registerWithParent, buildOptions } from '../core/utils.js';
+import { withProps } from '../core/with-props.js';
 
 import {
   createChildRegisterHandler,
@@ -7,7 +8,7 @@ import {
   LeafletRegisterEvent,
 } from '../core/register.js';
 import { isPathStyleAttr, updatePathStyle } from '../core/path-style.js';
-import type { PropDef, PropTypesFromTable } from '../types/props.js';
+import type { PropDef } from '../types/props.js';
 
 const PROPS = {
   lat: { kind: 'num', attr: 'lat', default: 0 },
@@ -21,22 +22,11 @@ const PROPS = {
   fillOpacity: { kind: 'num', attr: 'fill-opacity', default: 0.2 },
 } satisfies Record<string, PropDef>;
 
-type PropTypes = PropTypesFromTable<typeof PROPS>;
-const TypedBase = HTMLElement as unknown as new () => HTMLElement & PropTypes;
-
-export class LeafletCircleMarker extends TypedBase {
+export class LeafletCircleMarker extends withProps(HTMLElement, PROPS) {
   #obj?: CircleMarker;
   #children = new Map<HTMLElement, ChildEntry>();
   #childHandler?: (e: LeafletRegisterEvent) => void;
 
-  static get observedAttributes() {
-    return Object.values(PROPS).map((s) => s.attr);
-  }
-
-  static {
-    definePropAccessors(LeafletCircleMarker.prototype, PROPS);
-  }
-
   connectedCallback() {
     this.#obj = new CircleMarker(
       [this.#num('lat'), this.#num('lng')],

src/components/leaflet-circle.ts

@@ -1,5 +1,6 @@
 import { Circle } from 'leaflet';
-import { registerWithParent, buildOptions, definePropAccessors } from '../core/utils.js';
+import { registerWithParent, buildOptions } from '../core/utils.js';
+import { withProps } from '../core/with-props.js';
 
 import {
   createChildRegisterHandler,
@@ -7,7 +8,7 @@ import {
   type LeafletRegisterEvent,
 } from '../core/register.js';
 import { isPathStyleAttr, updatePathStyle } from '../core/path-style.js';
-import type { PropDef, PropTypesFromTable } from '../types/props.js';
+import type { PropDef } from '../types/props.js';
 
 const PROPS = {
   lat: { kind: 'num', attr: 'lat', default: 0 },
@@ -21,22 +22,11 @@ const PROPS = {
   fillOpacity: { kind: 'num', attr: 'fill-opacity', default: 0.2 },
 } satisfies Record<string, PropDef>;
 
-type PropTypes = PropTypesFromTable<typeof PROPS>;
-const TypedBase = HTMLElement as unknown as new () => HTMLElement & PropTypes;
-
-export class LeafletCircle extends TypedBase {
+export class LeafletCircle extends withProps(HTMLElement, PROPS) {
   #obj?: Circle;
   #children = new Map<HTMLElement, ChildEntry>();
   #childHandler?: (e: LeafletRegisterEvent) => void;
 
-  static get observedAttributes() {
-    return Object.values(PROPS).map((s) => s.attr);
-  }
-
-  static {
-    definePropAccessors(LeafletCircle.prototype, PROPS);
-  }
-
   connectedCallback() {
     this.#obj = new Circle(
       [this.#num('lat'), this.#num('lng')],

src/components/leaflet-control-attribution.ts

@@ -1,27 +1,17 @@
 import { Control, ControlPosition } from 'leaflet';
-import { registerWithParent, definePropAccessors } from '../core/utils.js';
+import { registerWithParent } from '../core/utils.js';
+import { withProps } from '../core/with-props.js';
 
-import type { PropDef, PropTypesFromTable } from '../types/props.js';
+import type { PropDef } from '../types/props.js';
 
 const PROPS = {
   position: { kind: 'str', attr: 'position', default: 'bottomright' },
   prefix: { kind: 'str', attr: 'prefix', default: '' },
 } satisfies Record<string, PropDef>;
 
-type PropTypes = PropTypesFromTable<typeof PROPS>;
-const TypedBase = HTMLElement as unknown as new () => HTMLElement & PropTypes;
-
-export class LeafletControlAttribution extends TypedBase {
+export class LeafletControlAttribution extends withProps(HTMLElement, PROPS) {
   #obj?: Control.Attribution;
 
-  static get observedAttributes() {
-    return Object.values(PROPS).map((s) => s.attr);
-  }
-
-  static {
-    definePropAccessors(LeafletControlAttribution.prototype, PROPS);
-  }
-
   connectedCallback() {
     this.#obj = new Control.Attribution({
       position: this.getAttribute('position') as ControlPosition | undefined,

src/components/leaflet-control-scale.ts

@@ -1,7 +1,8 @@
 import { Control, ControlPosition } from 'leaflet';
-import { registerWithParent, definePropAccessors } from '../core/utils.js';
+import { registerWithParent } from '../core/utils.js';
+import { withProps } from '../core/with-props.js';
 
-import type { PropDef, PropTypesFromTable } from '../types/props.js';
+import type { PropDef } from '../types/props.js';
 
 const PROPS = {
   position: { kind: 'str', attr: 'position', default: 'bottomleft' },
@@ -11,20 +12,9 @@ const PROPS = {
   updateWhenIdle: { kind: 'bool-on', attr: 'update-when-idle' },
 } satisfies Record<string, PropDef>;
 
-type PropTypes = PropTypesFromTable<typeof PROPS>;
-const TypedBase = HTMLElement as unknown as new () => HTMLElement & PropTypes;
-
-export class LeafletControlScale extends TypedBase {
+export class LeafletControlScale extends withProps(HTMLElement, PROPS) {
   #obj?: Control.Scale;
 
-  static get observedAttributes() {
-    return Object.values(PROPS).map((s) => s.attr);
-  }
-
-  static {
-    definePropAccessors(LeafletControlScale.prototype, PROPS);
-  }
-
   connectedCallback() {
     this.#obj = new Control.Scale({
       position: this.getAttribute('position') as ControlPosition | undefined,

src/components/leaflet-control-zoom.ts

@@ -1,7 +1,8 @@
 import { Control, ControlPosition } from 'leaflet';
-import { registerWithParent, definePropAccessors } from '../core/utils.js';
+import { registerWithParent } from '../core/utils.js';
+import { withProps } from '../core/with-props.js';
 
-import type { PropDef, PropTypesFromTable } from '../types/props.js';
+import type { PropDef } from '../types/props.js';
 
 const PROPS = {
   position: { kind: 'str', attr: 'position', default: 'topleft' },
@@ -11,20 +12,9 @@ const PROPS = {
   zoomOutTitle: { kind: 'str', attr: 'zoom-out-title', default: 'Zoom out' },
 } satisfies Record<string, PropDef>;
 
-type PropTypes = PropTypesFromTable<typeof PROPS>;
-const TypedBase = HTMLElement as unknown as new () => HTMLElement & PropTypes;
-
-export class LeafletControlZoom extends TypedBase {
+export class LeafletControlZoom extends withProps(HTMLElement, PROPS) {
   #obj?: Control.Zoom;
 
-  static get observedAttributes() {
-    return Object.values(PROPS).map((s) => s.attr);
-  }
-
-  static {
-    definePropAccessors(LeafletControlZoom.prototype, PROPS);
-  }
-
   connectedCallback() {
     this.#obj = new Control.Zoom({
       position: this.getAttribute('position') as ControlPosition | undefined,

src/components/leaflet-geojson.ts

@@ -1,12 +1,13 @@
 import { GeoJSON, PathOptions, Layer } from 'leaflet';
-import { buildOptions, registerWithParent, definePropAccessors } from '../core/utils.js';
+import { buildOptions, registerWithParent } from '../core/utils.js';
+import { withProps } from '../core/with-props.js';
 
 import {
   createChildRegisterHandler,
   type ChildEntry,
   LeafletRegisterEvent,
 } from '../core/register.js';
-import type { PropDef, PropTypesFromTable } from '../types/props.js';
+import type { PropDef } from '../types/props.js';
 
 const PROPS = {
   data: { kind: 'str', attr: 'data', default: '' },
@@ -28,22 +29,11 @@ const PROP_BY_ATTR = new Map<string, string>(
   Object.entries(PROPS).map(([name, spec]) => [spec.attr, name]),
 );
 
-type PropTypes = PropTypesFromTable<typeof PROPS>;
-const TypedBase = HTMLElement as unknown as new () => HTMLElement & PropTypes;
-
-export class LeafletGeoJSON extends TypedBase {
+export class LeafletGeoJSON extends withProps(HTMLElement, PROPS) {
   #obj?: GeoJSON;
   #children = new Map<HTMLElement, ChildEntry>();
   #childHandler?: (e: LeafletRegisterEvent) => void;
 
-  static get observedAttributes() {
-    return Object.values(PROPS).map((s) => s.attr);
-  }
-
-  static {
-    definePropAccessors(LeafletGeoJSON.prototype, PROPS);
-  }
-
   connectedCallback() {
     const raw = this.getAttribute('data');
     const data = raw ? JSON.parse(raw) : undefined;

src/components/leaflet-image-overlay.ts

@@ -1,17 +1,13 @@
 import { ImageOverlay, LatLngBounds, LatLngBoundsExpression, LatLngExpression } from 'leaflet';
-import {
-  registerWithParent,
-  buildOptions,
-  parseAttributeValue,
-  definePropAccessors,
-} from '../core/utils.js';
+import { registerWithParent, buildOptions, parseAttributeValue } from '../core/utils.js';
+import { withProps } from '../core/with-props.js';
 
 import {
   createChildRegisterHandler,
   type ChildEntry,
   LeafletRegisterEvent,
 } from '../core/register.js';
-import type { PropDef, PropTypesFromTable } from '../types/props.js';
+import type { PropDef } from '../types/props.js';
 
 const PROPS = {
   url: { kind: 'str', attr: 'url', default: '' },
@@ -29,22 +25,11 @@ const PROP_BY_ATTR = new Map<string, string>(
   Object.entries(PROPS).map(([name, spec]) => [spec.attr, name]),
 );
 
-type PropTypes = PropTypesFromTable<typeof PROPS>;
-const TypedBase = HTMLElement as unknown as new () => HTMLElement & PropTypes;
-
-export class LeafletImageOverlay extends TypedBase {
+export class LeafletImageOverlay extends withProps(HTMLElement, PROPS) {
   #obj?: ImageOverlay;
   #children = new Map<HTMLElement, ChildEntry>();
   #childHandler?: (e: LeafletRegisterEvent) => void;
 
-  static get observedAttributes() {
-    return Object.values(PROPS).map((s) => s.attr);
-  }
-
-  static {
-    definePropAccessors(LeafletImageOverlay.prototype, PROPS);
-  }
-
   connectedCallback() {
     const url = this.getAttribute('url') || '';
     this.#obj = new ImageOverlay(

src/components/leaflet-marker.ts

@@ -1,17 +1,13 @@
 import { Marker } from 'leaflet';
-import {
-  registerWithParent,
-  buildOptions,
-  parseAttributeValue,
-  definePropAccessors,
-} from '../core/utils.js';
+import { registerWithParent, buildOptions, parseAttributeValue } from '../core/utils.js';
+import { withProps } from '../core/with-props.js';
 
 import {
   createChildRegisterHandler,
   type ChildEntry,
   LeafletRegisterEvent,
 } from '../core/register.js';
-import type { PropDef, PropTypesFromTable } from '../types/props.js';
+import type { PropDef } from '../types/props.js';
 
 const PROPS = {
   lat: { kind: 'num', attr: 'lat', default: 0 },
@@ -27,22 +23,11 @@ const PROP_BY_ATTR = new Map<string, string>(
   Object.entries(PROPS).map(([name, spec]) => [spec.attr, name]),
 );
 
-type PropTypes = PropTypesFromTable<typeof PROPS>;
-const TypedBase = HTMLElement as unknown as new () => HTMLElement & PropTypes;
-
-export class LeafletMarker extends TypedBase {
+export class LeafletMarker extends withProps(HTMLElement, PROPS) {
   #obj?: Marker;
   #children = new Map<HTMLElement, ChildEntry>();
   #childHandler?: (e: LeafletRegisterEvent) => void;
 
-  static get observedAttributes() {
-    return Object.values(PROPS).map((s) => s.attr);
-  }
-
-  static {
-    definePropAccessors(LeafletMarker.prototype, PROPS);
-  }
-
   connectedCallback() {
     this.#obj = new Marker(
       [this.#num('lat'), this.#num('lng')],

src/components/leaflet-polygon.ts

@@ -1,5 +1,6 @@
 import { Polygon } from 'leaflet';
-import { registerWithParent, buildOptions, definePropAccessors } from '../core/utils.js';
+import { registerWithParent, buildOptions } from '../core/utils.js';
+import { withProps } from '../core/with-props.js';
 
 import {
   createChildRegisterHandler,
@@ -7,7 +8,7 @@ import {
   LeafletRegisterEvent,
 } from '../core/register.js';
 import { isPathStyleAttr, updatePathStyle } from '../core/path-style.js';
-import type { PropDef, PropTypesFromTable } from '../types/props.js';
+import type { PropDef } from '../types/props.js';
 import type { LeafletLine } from './leaflet-line.js';
 
 const PROPS = {
@@ -19,23 +20,12 @@ const PROPS = {
   fillOpacity: { kind: 'num', attr: 'fill-opacity', default: 0.2 },
 } satisfies Record<string, PropDef>;
 
-type PropTypes = PropTypesFromTable<typeof PROPS>;
-const TypedBase = HTMLElement as unknown as new () => HTMLElement & PropTypes;
-
-export class LeafletPolygon extends TypedBase {
+export class LeafletPolygon extends withProps(HTMLElement, PROPS) {
   #obj?: Polygon;
   #observer?: MutationObserver;
   #children = new Map<HTMLElement, ChildEntry>();
   #childHandler?: (e: LeafletRegisterEvent) => void;
 
-  static get observedAttributes() {
-    return Object.values(PROPS).map((s) => s.attr);
-  }
-
-  static {
-    definePropAccessors(LeafletPolygon.prototype, PROPS);
-  }
-
   connectedCallback() {
     this.#obj = new Polygon(this.#getCoords(), buildOptions(this, PROPS));
     this.#childHandler = createChildRegisterHandler(this.#obj, this.#children);

src/components/leaflet-polyline.ts

@@ -1,5 +1,6 @@
 import { Polyline } from 'leaflet';
-import { registerWithParent, buildOptions, definePropAccessors } from '../core/utils.js';
+import { registerWithParent, buildOptions } from '../core/utils.js';
+import { withProps } from '../core/with-props.js';
 
 import {
   createChildRegisterHandler,
@@ -7,7 +8,7 @@ import {
   LeafletRegisterEvent,
 } from '../core/register.js';
 import { isPathStyleAttr, updatePathStyle } from '../core/path-style.js';
-import type { PropDef, PropTypesFromTable } from '../types/props.js';
+import type { PropDef } from '../types/props.js';
 import type { LeafletLine } from './leaflet-line.js';
 
 const PROPS = {
@@ -19,23 +20,12 @@ const PROPS = {
   fillOpacity: { kind: 'num', attr: 'fill-opacity', default: 0.2 },
 } satisfies Record<string, PropDef>;
 
-type PropTypes = PropTypesFromTable<typeof PROPS>;
-const TypedBase = HTMLElement as unknown as new () => HTMLElement & PropTypes;
-
-export class LeafletPolyline extends TypedBase {
+export class LeafletPolyline extends withProps(HTMLElement, PROPS) {
   #obj?: Polyline;
   #observer?: MutationObserver;
   #children = new Map<HTMLElement, ChildEntry>();
   #childHandler?: (e: LeafletRegisterEvent) => void;
 
-  static get observedAttributes() {
-    return Object.values(PROPS).map((s) => s.attr);
-  }
-
-  static {
-    definePropAccessors(LeafletPolyline.prototype, PROPS);
-  }
-
   connectedCallback() {
     this.#obj = new Polyline(this.#getCoords(), buildOptions(this, PROPS));
     this.#childHandler = createChildRegisterHandler(this.#obj, this.#children);

src/components/leaflet-popup.ts

@@ -1,7 +1,8 @@
 import { Popup } from 'leaflet';
-import { registerWithParent, buildOptions, definePropAccessors } from '../core/utils.js';
+import { registerWithParent, buildOptions } from '../core/utils.js';
+import { withProps } from '../core/with-props.js';
 
-import type { PropDef, PropTypesFromTable } from '../types/props.js';
+import type { PropDef } from '../types/props.js';
 
 const PROPS = {
   lat: { kind: 'num', attr: 'lat', default: 0 },
@@ -14,21 +15,10 @@ const PROPS = {
   autoClose: { kind: 'bool-on', attr: 'auto-close' },
 } satisfies Record<string, PropDef>;
 
-type PropTypes = PropTypesFromTable<typeof PROPS>;
-const TypedBase = HTMLElement as unknown as new () => HTMLElement & PropTypes;
-
-export class LeafletPopup extends TypedBase {
+export class LeafletPopup extends withProps(HTMLElement, PROPS) {
   #obj?: Popup;
   #observer?: MutationObserver;
 
-  static get observedAttributes() {
-    return Object.values(PROPS).map((s) => s.attr);
-  }
-
-  static {
-    definePropAccessors(LeafletPopup.prototype, PROPS);
-  }
-
   connectedCallback() {
     this.#obj = new Popup({
       ...buildOptions(this, PROPS, ['lat', 'lng']),

src/components/leaflet-rectangle.ts

@@ -1,5 +1,6 @@
 import { Rectangle, LatLngBoundsExpression } from 'leaflet';
-import { registerWithParent, buildOptions, definePropAccessors } from '../core/utils.js';
+import { registerWithParent, buildOptions } from '../core/utils.js';
+import { withProps } from '../core/with-props.js';
 
 import {
   createChildRegisterHandler,
@@ -7,7 +8,7 @@ import {
   LeafletRegisterEvent,
 } from '../core/register.js';
 import { isPathStyleAttr, updatePathStyle } from '../core/path-style.js';
-import type { PropDef, PropTypesFromTable } from '../types/props.js';
+import type { PropDef } from '../types/props.js';
 
 const PROPS = {
   bounds: { kind: 'str', attr: 'bounds', default: '' },
@@ -19,22 +20,11 @@ const PROPS = {
   fillOpacity: { kind: 'num', attr: 'fill-opacity', default: 0.2 },
 } satisfies Record<string, PropDef>;
 
-type PropTypes = PropTypesFromTable<typeof PROPS>;
-const TypedBase = HTMLElement as unknown as new () => HTMLElement & PropTypes;
-
-export class LeafletRectangle extends TypedBase {
+export class LeafletRectangle extends withProps(HTMLElement, PROPS) {
   #obj?: Rectangle;
   #children = new Map<HTMLElement, ChildEntry>();
   #childHandler?: (e: LeafletRegisterEvent) => void;
 
-  static get observedAttributes() {
-    return Object.values(PROPS).map((s) => s.attr);
-  }
-
-  static {
-    definePropAccessors(LeafletRectangle.prototype, PROPS);
-  }
-
   connectedCallback() {
     this.#obj = new Rectangle(this.#parsedBounds(), buildOptions(this, PROPS, ['bounds']));
     this.#childHandler = createChildRegisterHandler(this.#obj, this.#children);

src/components/leaflet-svg-overlay.ts

@@ -1,17 +1,13 @@
 import { SVGOverlay, LatLngBounds, LatLngBoundsExpression, LatLngExpression } from 'leaflet';
-import {
-  registerWithParent,
-  buildOptions,
-  parseAttributeValue,
-  definePropAccessors,
-} from '../core/utils.js';
+import { registerWithParent, buildOptions, parseAttributeValue } from '../core/utils.js';
+import { withProps } from '../core/with-props.js';
 
 import {
   createChildRegisterHandler,
   type ChildEntry,
   LeafletRegisterEvent,
 } from '../core/register.js';
-import type { PropDef, PropTypesFromTable } from '../types/props.js';
+import type { PropDef } from '../types/props.js';
 
 const PROPS = {
   bounds: { kind: 'str', attr: 'bounds', default: '' },
@@ -26,22 +22,11 @@ const PROP_BY_ATTR = new Map<string, string>(
   Object.entries(PROPS).map(([name, spec]) => [spec.attr, name]),
 );
 
-type PropTypes = PropTypesFromTable<typeof PROPS>;
-const TypedBase = HTMLElement as unknown as new () => HTMLElement & PropTypes;
-
-export class LeafletSVGOverlay extends TypedBase {
+export class LeafletSVGOverlay extends withProps(HTMLElement, PROPS) {
   #obj?: SVGOverlay;
   #children = new Map<HTMLElement, ChildEntry>();
   #childHandler?: (e: LeafletRegisterEvent) => void;
 
-  static get observedAttributes() {
-    return Object.values(PROPS).map((s) => s.attr);
-  }
-
-  static {
-    definePropAccessors(LeafletSVGOverlay.prototype, PROPS);
-  }
-
   connectedCallback() {
     const svg = this.querySelector('svg');
     const dummy = !svg ? document.createElementNS('http://www.w3.org/2000/svg', 'svg') : undefined;

src/components/leaflet-tile-layer-wms.ts

@@ -1,17 +1,13 @@
 import { TileLayer } from 'leaflet';
-import {
-  registerWithParent,
-  buildOptions,
-  parseAttributeValue,
-  definePropAccessors,
-} from '../core/utils.js';
+import { registerWithParent, buildOptions, parseAttributeValue } from '../core/utils.js';
+import { withProps } from '../core/with-props.js';
 
 import {
   createChildRegisterHandler,
   type ChildEntry,
   LeafletRegisterEvent,
 } from '../core/register.js';
-import type { PropDef, PropTypesFromTable } from '../types/props.js';
+import type { PropDef } from '../types/props.js';
 
 const PROPS = {
   url: { kind: 'str', attr: 'url', default: '' },
@@ -27,22 +23,11 @@ const PROP_BY_ATTR = new Map<string, string>(
   Object.entries(PROPS).map(([name, spec]) => [spec.attr, name]),
 );
 
-type PropTypes = PropTypesFromTable<typeof PROPS>;
-const TypedBase = HTMLElement as unknown as new () => HTMLElement & PropTypes;
-
-export class LeafletTileLayerWMS extends TypedBase {
+export class LeafletTileLayerWMS extends withProps(HTMLElement, PROPS) {
   #obj?: TileLayer.WMS;
   #children = new Map<HTMLElement, ChildEntry>();
   #childHandler?: (e: LeafletRegisterEvent) => void;
 
-  static get observedAttributes() {
-    return Object.values(PROPS).map((s) => s.attr);
-  }
-
-  static {
-    definePropAccessors(LeafletTileLayerWMS.prototype, PROPS);
-  }
-
   connectedCallback() {
     const url = this.getAttribute('url') || '';
     this.#obj = new TileLayer.WMS(

src/components/leaflet-tile-layer.ts

@@ -1,17 +1,13 @@
 import { TileLayer } from 'leaflet';
-import {
-  registerWithParent,
-  buildOptions,
-  parseAttributeValue,
-  definePropAccessors,
-} from '../core/utils.js';
+import { registerWithParent, buildOptions, parseAttributeValue } from '../core/utils.js';
+import { withProps } from '../core/with-props.js';
 
 import {
   createChildRegisterHandler,
   type ChildEntry,
   LeafletRegisterEvent,
 } from '../core/register.js';
-import type { PropDef, PropTypesFromTable } from '../types/props.js';
+import type { PropDef } from '../types/props.js';
 
 const PROPS = {
   url: { kind: 'str', attr: 'url', default: '' },
@@ -26,22 +22,11 @@ const PROP_BY_ATTR = new Map<string, string>(
   Object.entries(PROPS).map(([name, spec]) => [spec.attr, name]),
 );
 
-type PropTypes = PropTypesFromTable<typeof PROPS>;
-const TypedBase = HTMLElement as unknown as new () => HTMLElement & PropTypes;
-
-export class LeafletTileLayer extends TypedBase {
+export class LeafletTileLayer extends withProps(HTMLElement, PROPS) {
   #obj?: TileLayer;
   #children = new Map<HTMLElement, ChildEntry>();
   #childHandler?: (e: LeafletRegisterEvent) => void;
 
-  static get observedAttributes() {
-    return Object.values(PROPS).map((s) => s.attr);
-  }
-
-  static {
-    definePropAccessors(LeafletTileLayer.prototype, PROPS);
-  }
-
   connectedCallback() {
     const url = this.getAttribute('url') || '';
     this.#obj = new TileLayer(url, buildOptions(this, PROPS, ['url']));

src/components/leaflet-tooltip.ts

@@ -1,7 +1,8 @@
 import { Tooltip } from 'leaflet';
-import { registerWithParent, buildOptions, definePropAccessors } from '../core/utils.js';
+import { registerWithParent, buildOptions } from '../core/utils.js';
+import { withProps } from '../core/with-props.js';
 
-import type { PropDef, PropTypesFromTable } from '../types/props.js';
+import type { PropDef } from '../types/props.js';
 
 const PROPS = {
   lat: { kind: 'num', attr: 'lat', default: 0 },
@@ -14,21 +15,10 @@ const PROPS = {
   opacity: { kind: 'num', attr: 'opacity', default: 1.0 },
 } satisfies Record<string, PropDef>;
 
-type PropTypes = PropTypesFromTable<typeof PROPS>;
-const TypedBase = HTMLElement as unknown as new () => HTMLElement & PropTypes;
-
-export class LeafletTooltip extends TypedBase {
+export class LeafletTooltip extends withProps(HTMLElement, PROPS) {
   #obj?: Tooltip;
   #observer?: MutationObserver;
 
-  static get observedAttributes() {
-    return Object.values(PROPS).map((s) => s.attr);
-  }
-
-  static {
-    definePropAccessors(LeafletTooltip.prototype, PROPS);
-  }
-
   connectedCallback() {
     this.#obj = new Tooltip({
       ...buildOptions(this, PROPS, ['lat', 'lng']),

src/components/leaflet-video-overlay.ts

@@ -1,17 +1,13 @@
 import { VideoOverlay, LatLngBounds, LatLngBoundsExpression, LatLngExpression } from 'leaflet';
-import {
-  registerWithParent,
-  buildOptions,
-  parseAttributeValue,
-  definePropAccessors,
-} from '../core/utils.js';
+import { registerWithParent, buildOptions, parseAttributeValue } from '../core/utils.js';
+import { withProps } from '../core/with-props.js';
 
 import {
   createChildRegisterHandler,
   type ChildEntry,
   LeafletRegisterEvent,
 } from '../core/register.js';
-import type { PropDef, PropTypesFromTable } from '../types/props.js';
+import type { PropDef } from '../types/props.js';
 
 const PROPS = {
   url: { kind: 'str', attr: 'url', default: '' },
@@ -30,22 +26,11 @@ const PROP_BY_ATTR = new Map<string, string>(
   Object.entries(PROPS).map(([name, spec]) => [spec.attr, name]),
 );
 
-type PropTypes = PropTypesFromTable<typeof PROPS>;
-const TypedBase = HTMLElement as unknown as new () => HTMLElement & PropTypes;
-
-export class LeafletVideoOverlay extends TypedBase {
+export class LeafletVideoOverlay extends withProps(HTMLElement, PROPS) {
   #obj?: VideoOverlay;
   #children = new Map<HTMLElement, ChildEntry>();
   #childHandler?: (e: LeafletRegisterEvent) => void;
 
-  static get observedAttributes() {
-    return Object.values(PROPS).map((s) => s.attr);
-  }
-
-  static {
-    definePropAccessors(LeafletVideoOverlay.prototype, PROPS);
-  }
-
   connectedCallback() {
     const url = this.getAttribute('url') || '';
     this.#obj = new VideoOverlay(

src/core/with-props.ts

@@ -0,0 +1,21 @@
+import type { PropDef, PropTypesFromTable } from '../types/props.js';
+import { definePropAccessors } from './utils.js';
+
+// eslint-disable-next-line @typescript-eslint/no-explicit-any
+type Ctor<T = object> = new (...args: any[]) => T;
+
+export function withProps<TBase extends Ctor<HTMLElement>, TProps extends Record<string, PropDef>>(
+  Base: TBase,
+  props: TProps,
+): TBase & Ctor<HTMLElement & PropTypesFromTable<TProps>> {
+  class WithProps extends Base {
+    static {
+      definePropAccessors(WithProps.prototype, props);
+    }
+    static get observedAttributes(): string[] {
+      return Object.values(props).map((s) => s.attr);
+    }
+  }
+
+  return WithProps as TBase & Ctor<HTMLElement & PropTypesFromTable<TProps>>;
+}

src/index.ts

@@ -1,4 +1,5 @@
 export * from './core/utils.js';
+export * from './core/with-props.js';
 export * from './core/path-style.js';
 export * from './core/register.js';
 export * from './types/props.js';