Localization & i18n — Advanced | Document Stack Docs

Overview

Document Stack supports generating documents in any language. Since templates use data binding, localization is handled through the data you pass to the API — the template stays the same, and the content adapts based on your data.

Language Through Data

The simplest approach is to pass localized strings in your API data:

English data

{
  "invoiceTitle": "Invoice",
  "dateLabel": "Date",
  "totalLabel": "Total",
  "customerName": "John Smith",
  "invoiceDate": "January 15, 2025",
  "total": "$1,250.00"
}

German data

{
  "invoiceTitle": "Rechnung",
  "dateLabel": "Datum",
  "totalLabel": "Gesamt",
  "customerName": "Hans Müller",
  "invoiceDate": "15. Januar 2025",
  "total": "1.250,00 €"
}

The same template works for both — field elements display whatever text you send.

Date Formatting

Format dates on the client side before sending to the API. Different locales expect different formats:

Locale	Format	Example
US English	MM/DD/YYYY	01/15/2025
UK English	DD/MM/YYYY	15/01/2025
German	DD.MM.YYYY	15.01.2025
Japanese	YYYY年MM月DD日	2025年01月15日
ISO	YYYY-MM-DD	2025-01-15

Format dates per locale

const date = new Date("2025-01-15");

// US English
date.toLocaleDateString("en-US"); // "1/15/2025"

// German
date.toLocaleDateString("de-DE"); // "15.1.2025"

// Japanese
date.toLocaleDateString("ja-JP"); // "2025/1/15"

// Long format
date.toLocaleDateString("en-US", {
    year: "numeric",
    month: "long",
    day: "numeric",
}); // "January 15, 2025"

Currency Formatting

Currency symbols and number formatting vary by locale:

Format currencies

const amount = 1250.5;

// US Dollar
new Intl.NumberFormat("en-US", {
    style: "currency",
    currency: "USD",
}).format(amount); // "$1,250.50"

// Euro (German)
new Intl.NumberFormat("de-DE", {
    style: "currency",
    currency: "EUR",
}).format(amount); // "1.250,50 €"

// Japanese Yen
new Intl.NumberFormat("ja-JP", {
    style: "currency",
    currency: "JPY",
}).format(amount); // "￥1,251"

// Indian Rupee
new Intl.NumberFormat("en-IN", {
    style: "currency",
    currency: "INR",
}).format(amount); // "₹1,250.50"

Number Formatting

Thousands separators and decimal points differ across locales:

Locale	Thousands	Decimal	Example
US/UK	,	.	1,250.50
Germany/France	.	,	1.250,50
Switzerland	'	.	1'250.50
India	,	.	1,250.50

Use Intl API

Always use JavaScript's built-in Intl.NumberFormat and Intl.DateTimeFormat for formatting. They handle locale-specific rules automatically.

Multi-Language Templates

You have two approaches for supporting multiple languages:

One template, localized data — Use field elements for all text (including labels) and pass translated strings in the data. Best for simple documents.
Per-language templates — Create separate templates for each language with static text in the local language. Best when layout changes significantly.

Font Support for Non-Latin Scripts

When generating documents in languages with non-Latin scripts, ensure your template uses fonts that support those characters:

CJK (Chinese, Japanese, Korean) — Use Noto Sans CJK or similar
Arabic / Hebrew — Use fonts with RTL support
Devanagari (Hindi) — Use Noto Sans Devanagari
Thai — Use Noto Sans Thai

Character Support

If characters appear as boxes or question marks in the generated PDF, the selected font doesn't support those characters. Switch to a font with the required character set.

Next Steps

Custom Fonts — Add fonts for different scripts
Data Formatting — Format values in templates
Data Binding — Connect data to templates

Localization & Internationalization