XLSX Templates

XLSX templates produce data-driven spreadsheets. Keep them native for analysts who'll keep editing, or convert to PDF for a frozen report. Velkin fills Handlebars placeholders in the workbook's OOXML, mirroring the DOCX pipeline.

Asset extension	.xlsx
Engine	Handlebars.js 4.7.8 (goja VM), preprocessed per cell
Renderer	Native fill, or LibreOffice (soffice) → PDF
Endpoints	render-xlsx (native), render-pdf (converted)

How it works

An .xlsx is OOXML in a ZIP. Velkin renders the parts that hold visible text:

• xl/sharedStrings.xml — the shared string table most cell text lives in. A {{tag}} typed into a cell usually lands here.
• xl/worksheets/sheet*.xml — sheet data, including cells stored as inline strings (t="inlineStr").

As with DOCX, tags split across formatting runs inside a shared string are rejoined before substitution.

Cell placeholders

Type Handlebars tags into cells:

	A	B
1	Customer	{{customer.name}}
2	Total	{{total}}

Dotted paths work for nested data ({{customer.address.city}}).

Loops are cell-level

No automatic row expansion

Unlike DOCX, XLSX templates do not promote {{#each}} to repeat whole rows. Excel renumbers and reflows duplicated rows, which produces noisy, broken output, so row-level promotion is intentionally disabled.

Express repetition at the cell-text level instead — build the repeated string inside a single cell, or pre-shape your data so each value maps to a known cell. For genuinely variable-length tables, the DOCX format (which does support row loops) is usually the better fit today.

A cell-level loop builds one string in one cell:

{{#each items}}{{description}}: {{amount}}€  {{/each}}

Formulas

Formulas authored in the template are preserved — Velkin only substitutes the text it finds in the string tables, it doesn't touch the formula definitions. A cell whose value is computed by a formula recalculates when the workbook is opened (or during PDF conversion).

Helpers & partials

The report's helpers.hbs works in cell text just like in the other formats: it's JavaScript, so register helpers and partials with Handlebars.registerHelper / Handlebars.registerPartial — see Helpers & Partials. As with DOCX, Handlebars escaping is disabled here because the workbook XML is already entity-encoded.

Native vs PDF output

• render-xlsx returns the filled-in .xlsx — editable, formulas intact.
• render-pdf converts the filled workbook to PDF with LibreOffice. The print area, page setup, and scaling configured in the workbook drive the resulting layout.

In the Studio, preferredOutput (native / pdf) only picks which endpoint the download button calls — see Output formats.