TutorialFebruary 28, 2026·2 min read

Building a Document Template System with React

How to create a document template system using docx-js-editor. Define DOCX templates with variable placeholders, fill them with data, and generate documents programmatically.

What is a document template system?

A document template system lets you:

  1. Create a DOCX template with placeholders like {customer_name} or {invoice_date}
  2. Fill those placeholders with real data from your application
  3. Generate completed documents ready for download or email

This is the backbone of document automation in legal tech, HR, finance, and any industry that produces standardized documents at scale.

Why build it in the browser?

Traditional template engines run on the server — you upload a template, send data via API, and get back a filled PDF or DOCX. This works, but:

  • Adds server cost for document processing
  • Creates latency — round-trip to the server for every document
  • Raises privacy concerns — sensitive data travels over the network
  • Requires backend infrastructure — more moving parts to maintain

With docx-js-editor, the entire workflow runs in the browser. Templates are parsed and filled client-side. No data leaves the user's machine.

Setting up the template editor

First, install the package:

npm install @eigenpal/docx-js-editor

Create a template editor component that lets users design templates visually:

import { useState } from "react";
import { DocxEditor } from "@eigenpal/docx-js-editor";
 
export function TemplateEditor() {
  const [buffer, setBuffer] = useState<ArrayBuffer | null>(null);
 
  const handleUpload = (e: React.ChangeEvent<HTMLInputElement>) => {
    const file = e.target.files?.[0];
    if (!file) return;
    const reader = new FileReader();
    reader.onload = () => setBuffer(reader.result as ArrayBuffer);
    reader.readAsArrayBuffer(file);
  };
 
  return (
    <div>
      <input type="file" accept=".docx" onChange={handleUpload} />
      {buffer && (
        <DocxEditor
          documentBuffer={buffer}
          onSave={(blob) => {
            // Save the template
            const url = URL.createObjectURL(blob);
            const a = document.createElement("a");
            a.href = url;
            a.download = "template.docx";
            a.click();
            URL.revokeObjectURL(url);
          }}
        />
      )}
    </div>
  );
}

Defining template variables

docx-js-editor uses docxtemplater under the hood. Placeholders use single curly braces:

Dear {recipient_name},

This agreement is entered into on {agreement_date} between
{company_name} ("Company") and {client_name} ("Client").

The total value of this agreement is {currency}{amount}.

You can detect all variables in a template programmatically using the detectVariables() utility, which scans the document body, headers, footers, footnotes, and text boxes.

Use cases

Law firms generate hundreds of contracts, NDAs, and agreements. Template variables typically include:

  • Party names and addresses
  • Dates (execution, effective, expiration)
  • Financial terms (amounts, percentages)
  • Jurisdiction-specific clauses

HR and onboarding

HR departments use templates for:

  • Offer letters
  • Employment contracts
  • Benefits enrollment forms
  • Policy acknowledgments

Finance and invoicing

Finance teams template:

  • Invoices with line items
  • Purchase orders
  • Financial reports
  • Tax documents

Best practices

Keep templates simple

Templates should be maintainable. Avoid deeply nested conditionals. If a template gets too complex, split it into multiple templates.

Version your templates

Store templates in version control or a document management system. When regulations change or terms update, you need to know which version was used for each generated document.

Validate before generating

Check that all required variables have values before generating a document. Missing placeholders in a final document look unprofessional and can have legal implications.

Test with edge cases

Test templates with:

  • Very long names that might break table layouts
  • Special characters (accents, symbols)
  • Empty optional fields
  • Multiple pages of repeated data

Next steps