export-kit

Simple, schema-driven data export library for TypeScript.

export-kit helps you transform JavaScript objects into structured text formats such as CSV and fixed-length records, then write them efficiently to files. It is designed for batch jobs, scheduled exports, banking files, legacy integrations, reporting, and ETL pipelines.

Unlike full ETL frameworks, export-kit focuses on one responsibility:

Convert objects into export formats with minimal code.

Features

• CSV export
• Fixed-length record export
• Schema-driven formatting
• Custom field formatting
• File writing utilities
• Streaming support
• Async file reader
• Date and time helpers
• Zero runtime dependencies
• Fully written in TypeScript

Why export-kit?

Many Node.js libraries can write files.

Many libraries can generate CSV.

Few libraries provide a reusable export framework.

export-kit separates how data is formatted from how data is written, making export logic reusable across applications.

 Business Object
        │
        ▼
 Export Formatter
        │
        ▼
  Formatted Text
        │
        ▼
   File Writer
        │
        ▼
     Output

This separation allows the same business object to be exported into different formats without changing business logic.

Supported Export Formats

CSV

   User
     │
     ▼
CSVFormatter
     │
     ▼
 CSV Text

Supports:

• Configurable separators
• Automatic escaping
• ISO date formatting
• Custom field formatting

Fixed-Length Records

       User
         │
         ▼
FixedLengthFormatter
         │
         ▼
 Fixed-Length Text

Supports:

• Configurable field widths
• Automatic padding
• Custom formatting
• Banking and legacy system exports

Architecture

                    Attributes
                         │
         ┌───────────────┴───────────────┐
         │                               │
         ▼                               ▼
  CSVFormatter                FixedLengthFormatter
         │                               │
         └───────────────┬───────────────┘
                         │
                  Formatted String
                         │
                 Stream File Writer 
                         │
                         ▼
                    Output File

The formatter is responsible only for converting objects into text.

The writer is responsible only for writing text.

This separation keeps export logic independent from file I/O.

Schema-Driven Formatting

Instead of manually building CSV strings, define a schema describing how each field should be exported.

const attributes = {
  id: {},
  name: {},
  birthday: {},
  salary: {
    getString: value => `$${value}`
  }
}

The formatter automatically converts each object according to the schema.

Benefits include:

• Reusable export definitions
• Centralized formatting rules
• Consistent exports
• Easier maintenance

Custom Field Formatting

Each attribute may define its own formatter.

Database Value

      1000
        │
        ▼
   getString()
        │
        ▼
     "$1000"

This makes it easy to customize:

• Currency
• Dates
• Enums
• Booleans
• Identifiers

without changing export logic.

CSV Escaping

CSV fields are automatically escaped when necessary.

Supports values containing:

• Separators
• Quotation marks
• Carriage returns
• Newlines

This ensures generated CSV files remain compatible with standard spreadsheet applications.

File Writing

export-kit provides lightweight file writing utilities suitable for batch processing.

Formatter
    │
    ▼
FileWriter
    │
    ▼
  Disk

For logging scenarios, LogWriter provides buffered writing with configurable line endings.

Streaming Support

Large exports can be written incrementally instead of generating the entire file in memory.

  Object
     │
     ▼
 Formatter
     │
     ▼
Write Stream
     │
     ▼
    File

This approach is suitable for exporting millions of records while keeping memory usage low.

Utility Functions

The library also includes small helpers commonly used in export jobs:

• Date formatting
• Time formatting
• Filename date extraction
• Date arithmetic
• Directory creation
• Async line reader

These utilities support typical batch-processing workflows without introducing additional dependencies.

Typical Use Cases

• Scheduled data exports
• CSV report generation
• Banking files
• Payroll exports
• Legacy system integration
• ETL pipelines
• Data migration
• Batch processing
• Regulatory reporting
• Enterprise data exchange

Design Principles

export-kit is built around a few simple principles:

• Single responsibility
• Schema-driven formatting
• Small, composable APIs
• Reusable export definitions
• Minimal dependencies
• Type-safe interfaces
• Production-ready performance

When to Use export-kit

Choose export-kit when you need to:

• Export business objects to CSV
• Generate fixed-length files
• Centralize export rules
• Build reusable export pipelines
• Process large datasets efficiently

If you need a lightweight, focused library for object-to-file export, export-kit provides the essential building blocks without requiring a full ETL framework.

License

MIT