Handlebars Pure Patterns

Handlebars Templating Standards

The "Logic-less" Philosophy

1. Data Preparation: Templates should strictly DISPLAY data. All filtering, sorting, or complex math MUST happen in the application code (Controller/Service) before the data reaches the template.
2. Avoid Spaghettis: If you need more than two nested {{#if}} or {{#each}} blocks, consider refactoring the data structure or creating a custom helper.

Syntax & Helpers

1. Escaping:
   • Default {{ value }} is safe and escapes HTML characters.
   • Use {{{ value }}} (triple-stash) ONLY for trusted HTML strings (e.g., pre-sanitized content).
2. Custom Helpers:
   • Do not write complex inline logic. Instead of {{#if (eq (mod index 2) 0)}}, create a helper {{#if (isEven index)}} or, better yet, pre-calculate isEven in the data model.
   • Register helpers for formatting dates, currencies, and translation.

Component Architecture (Partials)

1. Atomic Design: Break complex UIs into small files in the partials/ directory.
   • Naming convention: _card.hbs, _navbar.hbs.
2. Context Passing:
   • Explicit Context: {{> myPartial specificData }} is preferred over implicit context inheritance.
   • Block Partials: Use {{#> layout}} ... {{/layout}} for wrapping content (like slots).

Troubleshooting

• Missing Properties: Handlebars fails silently on undefined properties. Ensure your data object structure strictly matches the template expectations.
• Prototypes: If using Mongoose/ORMs, convert documents to Plain Old JavaScript Objects (POJOs) (e.g., .lean() or .toJSON()) before passing to Handlebars to avoid prototype access issues.

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