Overview

ClientExcelExporter is a client-side Excel report generator for OutSystems Reactive Applications, built on top of ExcelJS and executed entirely in the browser using JavaScript.
It converts JSON data into a professionally formatted Excel file, supporting branding, dynamic headers, automatic column detection, and performance-oriented client-side execution.

No server actions are required.

Key Features

• 100% client-side execution (no server load)

• Fast Excel generation using browser memory

• JSON key-value input with automatic structure flattening

• Automatic column detection and sizing

• Optional logo insertion

• Custom project name and report title

• Date column auto-detection and formatting

• Frozen header row and Excel filters

• Alternating row styles for readability

Inputs

JSON (Text – Required)

JSON array containing the data to be exported.

Example

[
  {
    "SupplierName": "ABC Ltd",
    "CreatedAt": "2025-01-10",
    "Address": {
      "City": "São Paulo",
      "Country": "Brazil"
    }
  }
]

Nested objects are automatically flattened into columns.

ProjectName (Text – Optional)

Displayed as the main header of the Excel file.

ExcelTitle (Text – Optional)

Displayed as a subtitle below the project name.

Filename (Text – Required)

Name of the generated Excel file (without .xlsx).

Logo (Binary / Base64 – Optional)

Company or project logo displayed at the top-left of the report.

Supported formats

• PNG

Taking this list of products as example, when clicking on the Export Excel button, the export result is available the next image;

Output

• Automatically downloads a .xlsx Excel file

• Fully formatted and ready for business use

Data Processing Details

JSON Flattening

Nested objects are flattened using _ as separator:

{
  "Address": {
    "City": "Rio",
    "Country": "BR"
  }
}

Becomes:

Address_City
Address_Country

Column Detection

• All keys across all objects are collected

• Columns are created dynamically

• Missing values are handled gracefully

Column Width Inference

Column width is calculated based on:

• Header text length

• Sample data values (first 50 rows)

This ensures readability without manual configuration.

Date Column Detection

A column is automatically formatted as a date when:

• The column name contains keywords like:
  date, created, updated, issued, delivery, etc.

• Sample values match common date formats

Applied Excel format

mm/dd/yyyy

Styling and UX Enhancements

• Bold and shaded header row

• Alternating row background colors

• Text wrapping enabled

• Vertical and horizontal alignment

• Thin row separators

• Auto-filter enabled on header

• Header row frozen for scrolling

Performance Notes

• Entirely client-side

• No round trips to the server

• Best suited for small to medium datasets

• Recommended logo size: < 500 KB

Limitations

• ExcelJS supports only png and jpeg

• Very large datasets may impact browser memory

• SVG and WebP images are not supported

Typical Use Cases

• Operational reports

• Dashboards export

• Administrative data extraction

• Audit and compliance reports

• Customer-facing Excel downloads

Compatibility

• OutSystems Reactive Applications

• Modern browsers (Chrome, Edge, Firefox)

• No server actions required

Summary

ClientExcelExporter provides a fast, flexible, and enterprise-ready way to generate Excel reports directly in the browser, making it ideal for modern OutSystems applications that prioritize performance, scalability, and user experience.

Example of list to be exported:

Here is the final result.