Web Components

Web Component patterns for frontend interactivity in the Oh My Brand! WordPress FSE theme.

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When to Use

• Adding frontend interactivity to blocks (carousels, accordions, lightboxes)
• Creating reusable interactive components
• Handling user interactions (clicks, keyboard, touch)
• Managing component state on the frontend

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Reference Files

File	Purpose
OmbGalleryCarousel.ts	Full Web Component example (~200 lines)
view.ts	Web Component scaffold

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Custom Element Structure

class OmbGalleryCarousel extends HTMLElement {
    static observedAttributes = ['visible-images'];

    #gallery: HTMLElement | null = null;
    #items: NodeListOf<HTMLElement> | null = null;
    #currentIndex = 0;

    connectedCallback(): void {
        this.#readAttributes();
        this.#queryElements();
        this.#bindEvents();
        this.#initialize();
    }

    disconnectedCallback(): void {
        this.#unbindEvents();
    }

    attributeChangedCallback(
        name: string,
        oldValue: string | null,
        newValue: string | null
    ): void {
        if (oldValue === newValue) return;
        // Handle attribute change
    }
}

if (!customElements.get('omb-gallery-carousel')) {
    customElements.define('omb-gallery-carousel', OmbGalleryCarousel);
}

See OmbGalleryCarousel.ts for the complete implementation.

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Lifecycle Methods

connectedCallback

Called when element is added to the DOM:

connectedCallback(): void {
    this.#readAttributes();    // 1. Read attributes
    this.#queryElements();      // 2. Query child elements
    this.#bindEvents();         // 3. Bind events
    this.#initialize();         // 4. Initialize state
}

disconnectedCallback

Called when element is removed from the DOM:

disconnectedCallback(): void {
    this.#unbindEvents();
    if (this.#animationFrame) cancelAnimationFrame(this.#animationFrame);
    if (this.#debounceTimer) clearTimeout(this.#debounceTimer);
}

attributeChangedCallback

Called when observed attribute changes:

static observedAttributes = ['visible-images', 'autoplay'];

attributeChangedCallback(
    name: string,
    oldValue: string | null,
    newValue: string | null
): void {
    if (oldValue === newValue) return;

    switch (name) {
        case 'visible-images':
            this.#visibleImages = newValue ? parseInt(newValue, 10) : 3;
            this.#updateLayout();
            break;
        case 'autoplay':
            newValue !== null ? this.#startAutoplay() : this.#stopAutoplay();
            break;
    }
}

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Attribute Handling

Boolean Attributes

const hasAutoplay = this.hasAttribute('autoplay');
this.setAttribute('loading', '');     // Add
this.removeAttribute('loading');       // Remove
this.toggleAttribute('loading');       // Toggle

Value Attributes

const value = this.getAttribute('visible-images');
const parsed = value ? parseInt(value, 10) : 3;
this.setAttribute('visible-images', '4');

Data Attributes

const config = JSON.parse(this.dataset.config || '{}');
this.dataset.state = 'loading';

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Event Handling

Arrow Function Methods

Use arrow functions to preserve this context:

class OmbComponent extends HTMLElement {
    #handleClick = (event: MouseEvent): void => {
        event.preventDefault();
        this.#doSomething();
    };

    #bindEvents(): void {
        this.addEventListener('click', this.#handleClick);
    }

    #unbindEvents(): void {
        this.removeEventListener('click', this.#handleClick);
    }
}

Custom Events

this.dispatchEvent(
    new CustomEvent('omb-gallery:slide-change', {
        bubbles: true,
        detail: { index: this.#currentIndex, total: this.#items?.length ?? 0 },
    })
);

Event Delegation

#handleContainerClick = (event: MouseEvent): void => {
    const target = event.target as HTMLElement;
    const item = target.closest('[data-gallery-item]');
    if (item) this.#handleItemClick(item as HTMLElement);
};

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DOM Queries

Query and Cache Elements

#queryElements(): void {
    this.#container = this.querySelector('[data-container]');
    this.#items = this.querySelectorAll('[data-item]');
    this.#button = this.querySelector('button') as HTMLButtonElement | null;
}

Null Safety

// Guard clause
if (!this.#container) return;

// Optional chaining
this.#button?.click();

// Nullish coalescing
const count = this.#items?.length ?? 0;

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Accessibility

Live Regions

#announce(): void {
    if (!this.#liveRegion) return;
    this.#liveRegion.textContent = `Showing image ${this.#currentIndex + 1} of ${this.#items?.length}`;
}

Keyboard Navigation

#handleKeydown = (event: KeyboardEvent): void => {
    switch (event.key) {
        case 'ArrowLeft':
        case 'ArrowUp':
            event.preventDefault();
            this.#navigatePrevious();
            break;
        case 'ArrowRight':
        case 'ArrowDown':
            event.preventDefault();
            this.#navigateNext();
            break;
        case 'Escape':
            event.preventDefault();
            this.#close();
            break;
    }
};

Focus Management

#open(): void {
    this.#previousFocus = document.activeElement as HTMLElement;
    this.#dialog?.showModal();
    this.#dialog?.querySelector<HTMLElement>('button')?.focus();
}

#close(): void {
    this.#dialog?.close();
    this.#previousFocus?.focus();
}

Reduced Motion

#shouldReduceMotion(): boolean {
    return window.matchMedia('(prefers-reduced-motion: reduce)').matches;
}

#scrollToIndex(): void {
    const behavior = this.#shouldReduceMotion() ? 'auto' : 'smooth';
    this.#gallery?.scrollTo({ left: scrollLeft, behavior });
}

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Registration

Guard Against Re-registration

if (!customElements.get('omb-gallery-carousel')) {
    customElements.define('omb-gallery-carousel', OmbGalleryCarousel);
}

Naming Convention

Pattern	Example
Tag name	omb-{block-name}
Class name	Omb{BlockName}

Examples:

• omb-gallery-carousel → OmbGalleryCarousel
• omb-faq-accordion → OmbFaqAccordion

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Related Skills

• typescript-standards - TypeScript conventions
• html-standards - HTML accessibility
• vitest-testing - Testing Web Components
• native-block-development - Block structure
• block-scaffolds - Web Component template

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References

• MDN Web Components
• Custom Elements Spec
• Web Components Best Practices