Predict Data Types

The Problem

When users upload CSV or JSON files, everything arrives as strings.

TypeScript and JavaScript can't help you here:

// ❌ TypeScript only knows static types
const userInput = "test@example.com"; // TypeScript thinks: string
const csvValue = "2024-01-01"; // TypeScript thinks: string
const formData = "42"; // TypeScript thinks: string

// TypeScript CANNOT detect these are email, date, and number at runtime

This library solves that problem with runtime type detection:

const { infer } = require("predict-data-types");

infer("test@example.com"); // → 'email' ✅
infer("2024-01-01"); // → 'date' ✅
infer("42"); // → 'number' ✅
infer('11:59 PM'); // → 'time' ✅
infer(["true", "false", "true"]);
// → 'boolean' ✅

infer({ name: "Alice", age: "25", email: "alice@example.com" });
// → { name: 'string', age: 'number', email: 'email' } ✅

infer([
  { name: "Alice", age: "25" },
  { name: "Bob", age: "30" },
]);
// → { name: 'string', age: 'number' } ✅

One smart function. Any input type.

Zero-dependency package for automatic data type detection from strings, arrays, and JSON objects. Detects 20+ data types including primitives, emails, URLs, UUIDs, dates, time, IPs, colors, percentages, hashtags, mentions, currency, postal codes, and file paths.

💡 Important: This library performs runtime type detection on string values, not static type checking. TypeScript is a compile-time type system for your code structure - this library analyzes actual data content at runtime. They solve completely different problems!

Features

Smart Type Inference: One infer() function handles strings, arrays, objects, and arrays of objects
20 Data Types: Primitives plus emails, URLs, UUIDs, dates, IPs, colors, percentages, currency, hashtags, MAC addresses, mentions, CRON, emoji, postal codes, and file paths
JSON Schema Generation: Automatically generate JSON Schema from objects (compatible with Ajv, etc.)
Type Constants: Use DataTypes for type-safe comparisons instead of string literals
CSV Support: Parse comma-separated values with optional headers
Zero Dependencies: Completely standalone, no external packages
TypeScript Support: Full type definitions included
45+ Date Formats: Comprehensive date parsing including month names and timezones
Battle-Tested: 123 comprehensive test cases

Installation

npm install predict-data-types

Quick Examples

Real-world use cases showing what you can build:

📊 CSV Import Tool

// Auto-detect column types and transform data
const employees = parseCSV(file); // All values are strings
const schema = infer(employees);
// → { name: 'string', email: 'email', salary: 'currency', hire_date: 'date' }

🎨 Form Builder

// Auto-generate form fields with correct input types
const userData = { email: 'alice@example.com', age: '25', website: 'https://alice.dev' };
const types = infer(userData);
// → { email: 'email', age: 'number', website: 'url' }
// Generate: <input type="email">, <input type="number">, <input type="url">

🌐 API Analyzer

// Generate JSON Schema and TypeScript interfaces from API responses
const response = await fetch('/api/users').then(r => r.json());
const jsonSchema = infer(response, Formats.JSONSCHEMA);
// Use with Ajv, joi, or generate TypeScript types

✅ Data Validator

// Validate imported data quality
const expected = { email: DataTypes.EMAIL, age: DataTypes.NUMBER };
const actual = infer(importedData);
// Detect mismatches, missing fields, wrong types

👉 See full runnable examples in examples/ directory

Supported Data Types

Type	Examples
`string`	`'John'`, `'Hello World'`
`number`	`42`, `3.14`, `-17`, `1e10`
`boolean`	`true`, `false`, `yes`, `no`
`email`	`user@example.com`
`phone`	`555-555-5555`, `(555) 555-5555`
`url`	`https://example.com`
`uuid`	`550e8400-e29b-41d4-a716-446655440000`
`date`	`2023-12-31`, `31/12/2023`
`ip`	`192.168.1.1`, `2001:0db8::1`
`macaddress`	`00:1B:63:84:45:E6`, `00-1B-63-84-45-E6`
`color`	`#FF0000`, `#fff`, `rgb(255, 0, 0)`, `rgba(0, 255, 0, 0.5)`
`percentage`	`50%`, `-25%`
`currency`	`$100`, `€50.99`
`hashtag`	`#hello`, `#OpenSource`, `#dev_community`
`mention`	`@username`, `@user_name123`, `@john-doe`
`cron`	`0 0 * * `, `/5 * * * `, `0 9-17 * 1-5`
`emoji`	`😀`, `🎉`, `❤️`, `👍`, `❌`
`filepath`	`/usr/local/bin`, `C:\\Program Files\\node.exe`, `./src/index.js`
`isbn`	`978-0-596-52068-7`, `0596520689`, `043942089X`
`postcode`	`12345`, `12345-6789`, `SW1A 1AA`, `M5H 2N2`, `75001`
`array`	`[1, 2, 3]`
`object`	`{"name": "John"}`
`mime:image`	`image/png`, `image/jpeg`, `image/gif`, `image/svg+xml`
`mime:application`	`application/json`, `application/pdf`, `application/zip`
`mime:text`	`text/html`, `text/plain`, `text/css`, `text/javascript`
`mime:media`	`video/mp4`, `audio/mpeg`
`semver`	`0.0.0`
`time`	`23:59:59`, `2:30 PM`, `14:30`
`coordinate`	`40.7128, -74.0060`, `51.5074, -0.1278`

Usage

Type Constants (Recommended)

Use DataTypes constants instead of string literals for type-safe comparisons:

const { infer, DataTypes } = require("predict-data-types");

const type = infer("test@example.com");

// ✅ Type-safe with constants
if (type === DataTypes.EMAIL) {
  console.log("Valid email!");
}

// ❌ Avoid string literals (error-prone)
if (type === 'email') { ... }

// All available constants:
DataTypes.STRING      // 'string'
DataTypes.NUMBER      // 'number'
DataTypes.BOOLEAN     // 'boolean'
DataTypes.EMAIL       // 'email'
DataTypes.PHONE       // 'phone'
DataTypes.URL         // 'url'
DataTypes.UUID        // 'uuid'
DataTypes.DATE        // 'date'
DataTypes.ARRAY       // 'array'
DataTypes.OBJECT      // 'object'
DataTypes.IP          // 'ip'
DataTypes.MACADDRESS  // 'macaddress'
DataTypes.COLOR       // 'color'
DataTypes.PERCENTAGE  // 'percentage'
DataTypes.CURRENCY    // 'currency'
DataTypes.MENTION     // 'mention'
DataTypes.CRON        // 'cron'
DataTypes.HASHTAG     // 'hashtag'
// MIME types
DataTypes.MIME_IMAGE        // 'mime:image'
DataTypes.MIME_APPLICATION  // 'mime:application'
DataTypes.MIME_TEXT         // 'mime:text'
DataTypes.MIME_MEDIA        // 'mime:media'
DataTypes.EMOJI       // 'emoji'
DataTypes.FILEPATH    // 'filepath'
DataTypes.SEMVER      // 'semver'
DataTypes.TIME        // 'time'
DataTypes.ISBN        // 'isbn'
DataTypes.POSTCODE    // 'postcode'
DataTypes.COORDINATE  // 'coordinate'

Basic Example

const predictDataTypes = require("predict-data-types");

const text = "John, 30, true, john@example.com, 2023-01-01, 0.0.0";
const types = predictDataTypes(text);

console.log(types);
// {
//   'John': 'string',
//   '30': 'number',
//   'true': 'boolean',
//   'john@example.com': 'email',
//   '2023-01-01': 'date'
// 'image/png': 'mime:image',
// 'application/json': 'mime:application',
// 'text/html': 'mime:text',
//   '2023-01-01': 'date',
//   '0.0.0':'semver'
// }

Smart `infer()` Function

The infer() function automatically adapts to any input type:

const { infer, DataTypes } = require("predict-data-types");

// Single value → DataType
infer("2024-01-01"); // → 'date'
infer("12:05 AM"); // → 'time'
infer("test@example.com"); // → 'email'
infer("@username"); // → 'mention'
infer("42"); // → 'number'
infer("#OpenSource"); // → 'hashtag'
infer("/usr/local/bin"); // → 'filepath'
infer("40.7128, -74.0060"); // → 'coordinate'
infer(["#dev", "#opensource", "#community"]); // → 'hashtag'
// MIME types
infer('image/png');          // 'mime:image'
infer('image/jpeg');         // 'mime:image'
infer('application/json');   // 'mime:application'
infer('application/pdf');    // 'mime:application'
infer('text/html');          // 'mime:text'
infer('text/css');           // 'mime:text'
infer('video/mp4');          // 'mime:media'
infer('audio/mpeg');         // 'mime:media'

// Ambiguous 3-char values (can be hex color or hashtag)
infer("#bad"); // → 'color' (default: hex takes priority)
infer("#bad", "none", { preferHashtagOver3CharHex: true }); // → 'hashtag'

// Array of values → Common DataType
infer(["1", "2", "3"]); // → 'number'
infer(["true", "false", "yes"]); // → 'boolean'

// Object → Schema
infer({
  name: "Alice",
  age: "25",
  active: "true",
});
// → { name: 'string', age: 'number', active: 'boolean' }

// Array of objects → Schema
infer([
  { name: "Alice", age: "25", email: "alice@example.com" },
  { name: "Bob", age: "30", email: "bob@example.com" },
]);

// → { name: 'string', age: 'number', email: 'email' }

JSON Schema Format

Generate standard JSON Schema for validation libraries (Ajv, etc.):

const { infer, Formats } = require("predict-data-types");

const data = {
  name: "Alice",
  age: "25",
  email: "alice@example.com",
  website: "https://example.com",
};

// Simple format (default)
infer(data);
// → { name: 'string', age: 'number', email: 'email', website: 'url' }

// JSON Schema format
infer(data, Formats.JSONSCHEMA);
// → {
//     type: 'object',
//     properties: {
//       name: { type: 'string' },
//       age: { type: 'number' },
//       email: { type: 'string', format: 'email' },
//       website: { type: 'string', format: 'uri' }
//     },
//     required: ['name', 'age', 'email', 'website']
//   }

// Use with validation libraries
const Ajv = require("ajv");
const ajv = new Ajv();

const schema = infer(data, Formats.JSONSCHEMA);
const validate = ajv.compile(schema);
const valid = validate({
  name: "Bob",
  age: 30,
  email: "bob@example.com",
  website: "https://bob.dev",
});

CSV with Headers

const csvData = `name,age,active,email
John,30,true,john@example.com`;

const types = predictDataTypes(csvData, true);
// {
//   'name': 'string',
//   'age': 'number',
//   'active': 'boolean',
//   'email': 'email'
// }

📚 Complete Examples

The examples/ directory contains full, runnable code for real-world scenarios:

CSV Import - Parse CSV files, auto-detect types, transform data to proper JavaScript types
Form Builder - Dynamically generate HTML forms with correct input types and validation
API Analyzer - Generate JSON Schemas, TypeScript interfaces, and API documentation
Data Validation - Validate imported data quality and detect type mismatches

Each example includes:

✅ Complete runnable code with detailed comments
✅ Real-world use cases and scenarios
✅ Sample data files where applicable

Run any example:

cd examples/csv-import
node example.js

✅ Sample data files

Complex Data

const { infer } = require('predict-data-types');

const complexString = "192.168.1.1, #FF0000, 50%, $100, 2023-12-31";
const types = infer(complexString.split(', ').map(v => ({ value: v })));
// { value: 'ip' } // Takes the most specific type found

// Or analyze each value separately:
const values = "192.168.1.1, #FF0000, 50%, $100, 2023-12-31".split(', ');
values.forEach(val => {
  console.log(`${val}: ${infer(val)}`);
});
// 192.168.1.1: ip
// #FF0000: color
// 50%: percentage
// $100: currency
// 2023-12-31: date

API

`infer(input, format?, options?)`

The main function - handles any input type:

Parameters:

input (string | string[] | Object | Object[]): Value(s) to analyze
format (optional): Output format - Formats.NONE (default) or Formats.JSONSCHEMA
options (optional): Configuration options
- preferHashtagOver3CharHex (boolean, default: false): When true, treats ambiguous 3-character values like #bad, #ace as hashtags instead of hex colors

Returns:

DataType (string) - for single values and arrays of values
Schema (Object) - for objects and arrays of objects
JSONSchema (Object) - when format is Formats.JSONSCHEMA

Examples:

const { infer, Formats, DataTypes } = require('predict-data-types');

// Single values
infer("42"); // → 'number'
infer("test@example.com"); // → 'email'

// Arrays
infer(["1", "2", "3"]); // → 'number'

// Objects
infer({ age: "25", email: "test@example.com" });
// → { age: 'number', email: 'email' }

// Arrays of objects
infer([{ age: "25" }, { age: "30" }]);
// → { age: 'number' }

// JSON Schema format
infer({ name: "Alice", age: "25" }, Formats.JSONSCHEMA);
// → { type: 'object', properties: {...}, required: [...] }

// Hashtag field example
infer({ tag: "#OpenSource" }, Formats.JSONSCHEMA);
// {
//   tag: { type: 'string', pattern: '^#[A-Za-z0-9_]+$' }
// }

Constants

DataTypes - Type-safe constants for comparisons:

DataTypes.STRING, DataTypes.NUMBER, DataTypes.BOOLEAN, DataTypes.EMAIL,
DataTypes.PHONE, DataTypes.URL, DataTypes.UUID, DataTypes.DATE,
DataTypes.IP, DataTypes.COLOR, DataTypes.PERCENTAGE, DataTypes.CURRENCY, DataTypes.HASHTAG, DataTypes.FILEPATH,
DataTypes.ARRAY, DataTypes.OBJECT, DataTypes.SEMVER, DataTypes.TIME, DataTypes.ISBN, DataTypes.POSTCODE, DataTypes.COORDINATE

Formats - Output format constants:

Formats.NONE        // Default simple schema
Formats.JSONSCHEMA  // JSON Schema format

Legacy API

predictDataTypes(input, firstRowIsHeader) - For CSV strings only (use infer() instead)

Show legacy API details

Parameters:

input (string): Comma-separated string to analyze
firstRowIsHeader (boolean): Treat first row as headers (default: false)

Returns: Object mapping field names/values to their data types

Example:

const types = predictDataTypes('name,age\nAlice,25', true);
// { name: 'string', age: 'number' }

Note: This function is maintained for backwards compatibility. New code should use infer().

TypeScript vs. This Library

Common Misconception: "Doesn't TypeScript already do this?"

No! TypeScript and this library serve completely different purposes:

Feature	TypeScript	This Library
When it works	Compile-time	Runtime
What it checks	Your code structure	Actual data content
Scope	Static type annotations	Dynamic string analysis
Use case	Prevent coding errors	Analyze user-provided data

Example:

// TypeScript
const value: string = "test@example.com";
// TypeScript knows: "value is a string"
// TypeScript DOESN'T know: "value contains an email address"

// This Library
const type = infer("test@example.com");
// Returns: 'email' ✅
// Detects the ACTUAL CONTENT at runtime

When to use this library:

📊 Users upload CSV/Excel files
🌐 API responses with unknown structure
📝 Form data that needs validation
🔄 ETL pipelines processing raw data
🎨 Dynamic form/UI generation

TypeScript can't help with any of these - you need runtime type detection!

Development

npm test              # Run tests
npm run test:coverage # Run tests with coverage
npm run lint          # Check code quality
npm run lint:fix      # Fix lint issues

License

MIT License - see LICENSE file for details.

Contributing

See CONTRIBUTING.md for contribution guidelines.

Author: Melih Birim

Name		Name	Last commit message	Last commit date
Latest commit History 111 Commits
.github		.github
.husky		.husky
examples		examples
test		test
.gitignore		.gitignore
CONTRIBUTING.md		CONTRIBUTING.md
LICENSE		LICENSE
PR_37_FIXES.md		PR_37_FIXES.md
README.md		README.md
ROADMAP.md		ROADMAP.md
eslint.config.js		eslint.config.js
index.d.ts		index.d.ts
index.js		index.js
package-lock.json		package-lock.json
package.json		package.json
test-types.ts		test-types.ts

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Predict Data Types

The Problem

Features

Installation

Quick Examples

Supported Data Types

Usage

Type Constants (Recommended)

Basic Example

Smart `infer()` Function

JSON Schema Format

CSV with Headers

📚 Complete Examples

Complex Data

API

`infer(input, format?, options?)`

Constants

Legacy API

TypeScript vs. This Library

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Predict Data Types

The Problem

Features

Installation

Quick Examples

Supported Data Types

Usage

Type Constants (Recommended)

Basic Example

Smart infer() Function

JSON Schema Format

CSV with Headers

📚 Complete Examples

Complex Data

API

infer(input, format?, options?)

Constants

Legacy API

TypeScript vs. This Library

Development

License

Contributing

About

Resources

License

Contributing

Uh oh!

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Releases 6

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Smart `infer()` Function

`infer(input, format?, options?)`

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