Theme Shopify HTML Data Comments

Shopify HTML, Data Attributes & Comments

Guidelines for HTML structure, data attributes usage, and code commenting in Shopify themes.

When to Use

• Structuring HTML markup in sections
• Passing data to JavaScript via attributes
• Adding comments to Liquid templates
• Organizing HTML elements

HTML & Data Attributes

Custom HTML Tags

• Use custom HTML tags when appropriate
• Custom elements work well with JavaScript custom elements
• Improves semantic structure

Example

<product-card data-product-id="{{ product.id }}">
  <!-- Content -->
</product-card>

Data Attributes

• Pass dynamic data via data-* attributes
• Access in JavaScript via dataset property
• Use kebab-case for attribute names

Data Attribute Naming

<!-- Good - kebab-case -->
<div 
  data-product-id="{{ product.id }}"
  data-variant-id="{{ variant.id }}"
  data-product-handle="{{ product.handle }}">
</div>

<!-- Bad - camelCase or other formats -->
<div data-productId="{{ product.id }}"></div>

Accessing Data in JavaScript

class ProductCard extends HTMLElement {
  constructor() {
    super();
    this.productId = this.dataset.productId;
    this.variantId = this.dataset.variantId;
    this.productHandle = this.dataset.productHandle;
  }
}

Data Attributes for Configuration

Use data attributes to pass configuration from Liquid to JavaScript:

<image-gallery 
  data-autoplay="{{ section.settings.autoplay }}"
  data-interval="{{ section.settings.interval }}"
  data-transition="{{ section.settings.transition }}">
  <!-- Gallery content -->
</image-gallery>

class ImageGallery extends HTMLElement {
  constructor() {
    super();
    this.autoplay = this.dataset.autoplay === 'true';
    this.interval = parseInt(this.dataset.interval, 10);
    this.transition = this.dataset.transition;
  }
}

Comments

Comment Guidelines

• Keep comments minimal
• Comment only non-obvious logic
• Do NOT explain every line
• Use comments to explain "why", not "what"

Liquid Comments

{%- comment -%}
  Calculate discount percentage for products with compare_at_price.
  Only show discount badge if discount is greater than 20%.
{%- endcomment -%}

{% liquid
  if product.compare_at_price > product.price
    assign discount = product.compare_at_price | minus: product.price
    assign discount_percent = discount | times: 100 | divided_by: product.compare_at_price
    if discount_percent > 20
      assign show_badge = true
    endif
  endif
%}

Snippet Usage Comments

Always include usage comments in snippets:

{%- comment -%}
Usage:
{% render 'product-card', 
  product: product, 
  show_vendor: true, 
  show_price: true %}
{%- endcomment -%}

HTML Comments

Use HTML comments sparingly for section organization:

{%- comment -%}
  Product Card Section
  Displays product information with image, title, price, and add to cart button
{%- endcomment -%}

<div class="product-card">
  <!-- Product Image -->
  <div class="product-card__image">
    {{ product.featured_image | image_tag: widths: '360, 720', loading: 'lazy' }}
  </div>

  <!-- Product Info -->
  <div class="product-card__info">
    <h3 class="product-card__title">{{ product.title }}</h3>
    <p class="product-card__price">{{ product.price | money }}</p>
  </div>
</div>

When to Comment

Do comment:

• Complex business logic
• Non-obvious calculations
• Workarounds or hacks
• Snippet usage instructions
• Section-level documentation

Don't comment:

• Obvious code (e.g., {% if product.available %})
• Every line of code
• Self-explanatory variable names
• Standard Liquid syntax

Example: Good vs Bad Comments

{%- comment -%}
  Good: Explains why, not what
  Calculate discount percentage. Shopify doesn't provide this directly,
  so we calculate it from compare_at_price and current price.
{%- endcomment -%}
{% liquid
  assign discount = product.compare_at_price | minus: product.price
  assign discount_percent = discount | times: 100 | divided_by: product.compare_at_price
%}

{%- comment -%}
  Bad: Explains what, which is obvious
  Check if product is available. If available, show add to cart button.
{%- endcomment -%}
{% if product.available %}
  <button>Add to Cart</button>
{% endif %}

HTML Structure Best Practices

Semantic HTML

Use semantic HTML elements:

<article class="product-card">
  <header class="product-card__header">
    <h2 class="product-card__title">{{ product.title }}</h2>
  </header>
  <div class="product-card__image">
    {{ product.featured_image | image_tag: widths: '360, 720', loading: 'lazy' }}
  </div>
  <footer class="product-card__footer">
    <p class="product-card__price">{{ product.price | money }}</p>
    <button class="product-card__button">Add to Cart</button>
  </footer>
</article>

Accessibility

Include proper accessibility attributes:

<button 
  aria-label="Add {{ product.title }} to cart"
  data-product-id="{{ product.id }}">
  Add to Cart
</button>

Shopify Theme Documentation

Reference these official Shopify resources:

• HTML Elements
• Data Attributes
• Web Accessibility
• Shopify Theme Structure

Instructions

1. Use custom HTML tags when appropriate for semantic structure
2. Pass data via data-* attributes using kebab-case
3. Keep comments minimal - only for non-obvious logic
4. Comment "why", not "what" - explain reasoning, not obvious code
5. Include usage comments in all snippets
6. Use semantic HTML for better structure and accessibility
7. Add accessibility attributes (aria-label, alt text, etc.)