CSV Import Formatter

A web-based CSV column mapping and transformation tool built with Deno Fresh.

Features

• CSV Parsing: Upload or paste CSV data with automatic encoding detection (UTF-8, Windows-1252)
• Delimiter Detection: Auto-detect and configure input/output delimiters (comma, semicolon, tab)
• Column Mapping: Rename columns from source to target names
• Type Transformations: Convert column data types
  • string - Text (default)
  • integer - Whole numbers
  • number - Decimal numbers
  • boolean - Boolean values (outputs as 1/0 in CSV)
• Value Transformations:
  • uppercase / lowercase - Case conversion
  • trim - Remove whitespace
  • date - Date formatting with configurable source/target formats
• Value Conversions: Map specific values to other values (e.g., Mr → male, Ms → female)
• Number Conversion: Configurable decimal separator (period or comma), thousand separators automatically removed
• Import/Export: Save and load mapping configurations as JSON

Mapping Configuration Schema

{
  "version": "1.0",
  "inputDelimiter": "," | ";" | "\t",
  "outputDelimiter": "," | ";" | "\t",
  "decimalSeparator": "." | ",",
  "mappings": {
    "sourceColumn": "targetColumn"
  },
  "typeTransformations": {
    "column": "string | integer | number | boolean"
  },
  "transformations": {
    "column": "uppercase | lowercase | trim | date | date:sourceFormat | date:sourceFormat:targetFormat"
  },
  "valueConversions": {
    "column": { "sourceValue": "targetValue" }
  }
}

Type Transformations

Type	Description	Output
string	Text data (default)	As-is
integer	Whole numbers	Rounded, thousand separators removed
number	Decimal numbers	Thousand separators removed
boolean	Boolean values	1 or 0 in CSV output

Value Transformations

Transformation	Description	Example
uppercase	Convert to uppercase	hello → HELLO
lowercase	Convert to lowercase	HELLO → hello
trim	Remove whitespace	hello → hello
date	Auto-detect input, output yyyy-MM-dd	15/01/2024 → 2024-01-15
date:targetFormat	Auto-detect input, custom output	date:dd/MM/yyyy
date:sourceFormat:targetFormat	Explicit source and target	date:MM/dd/yyyy:yyyy-MM-dd

Auto-detected Date Formats

The following input formats are automatically detected (EU formats only):

• yyyy-MM-dd (ISO)
• dd/MM/yyyy
• dd-MM-yyyy
• dd.MM.yyyy
• yyyy/MM/dd

For US formats like MM/dd/yyyy, use explicit source format: date:MM/dd/yyyy:yyyy-MM-dd

Date Format Tokens

Token	Description	Example
yyyy	4-digit year	2024
MM	2-digit month	01-12
dd	2-digit day	01-31
HH	2-digit hour (24h)	00-23
mm	2-digit minute	00-59
ss	2-digit second	00-59

Invalid dates output an empty string.

Value Conversions

Map specific input values to output values. Matching is case-insensitive.

{
  "valueConversions": {
    "title": {
      "Mr": "male",
      "Ms": "female",
      "Mrs": "female"
    },
    "status": {
      "A": "Active",
      "I": "Inactive",
      "P": "Pending"
    }
  }
}

Input	Output
Mr	male
ms	female
MRS	female

Number Parsing

Numbers are parsed based on the configured decimal separator:

Decimal Separator	Input	Output
. (Period)	1,234.56	1234.56
, (Comma)	1.234,56	1234.56

Thousand separators are always removed. Output uses . as decimal separator.

Examples

The static/examples/ directory contains example CSV files with matching mapping configurations:

Example	Description
employees	EU format: numbers 1.234,56, dates dd/MM/yyyy → yyyy-MM-dd, title → gender (Mr → male)
products	Numbers 29.99, dates yyyy-MM-dd, availability (yes/no → 1/0)

Load examples directly from the UI using the "Load example" dropdown.

Example Structure

static/examples/
├── index.json           # Example registry
├── employees.csv        # Employee CSV data
├── employees.mapping.json
├── products.csv         # Product CSV data
└── products.mapping.json

Usage

Make sure to install Deno: https://docs.deno.com/runtime/getting_started/installation

Start the project in development mode:

deno task dev

This will watch the project directory and restart as necessary.

Schema

The full JSON Schema for mapping configurations is available at schemas/mapping.schema.json.