@dodysat/bmi

A comprehensive BMI (Body Mass Index) calculator library following WHO (World Health Organization) standards. This library provides accurate BMI calculations with proper categorization and health recommendations based on international guidelines.

Features

• ✅ WHO Standard Compliance: Follows World Health Organization BMI categories and thresholds
• ✅ TypeScript Support: Full TypeScript support with comprehensive type definitions
• ✅ Multiple Unit Support: Metric and Imperial unit conversions
• ✅ Health Recommendations: WHO-based health recommendations for each BMI category
• ✅ Input Validation: Robust input validation with helpful error messages
• ✅ Comprehensive Testing: 100% test coverage with edge case handling
• ✅ Multi-Language Support: English and Indonesian localization with easy extensibility

Installation

npm install @dodysat/bmi

Quick Start

import { calculateBMI, BMICategory } from '@dodysat/bmi';

// Calculate BMI for a person (70kg, 1.75m)
const result = calculateBMI({ weight: 70, height: 1.75 });

console.log(`BMI: ${result.bmi}`); // 22.86
console.log(`Category: ${result.categoryName}`); // "Normal Weight"
console.log(`Recommendations:`, result.recommendations);

// With Indonesian localization
const resultId = calculateBMI({ weight: 70, height: 1.75, locale: 'id' });
console.log(`Category: ${resultId.categoryName}`); // "Berat Badan Normal"

API Reference

Main Functions

calculateBMI(input: BMIInput): BMIResult

Calculates BMI using metric units (kilograms and meters).

import { calculateBMI } from '@dodysat/bmi';

const result = calculateBMI({ weight: 70, height: 1.75 });

Parameters:

• input.weight: Weight in kilograms (positive number)
• input.height: Height in meters (positive number)
• input.locale: Locale for localized output (optional, defaults to 'en')

Returns: BMIResult object with BMI value, category, and recommendations

calculateBMISimple(weight: number, height: number, locale?: Locale): BMIResult

Convenience function for calculating BMI with separate parameters.

import { calculateBMISimple } from '@dodysat/bmi';

const result = calculateBMISimple(70, 1.75);
const resultId = calculateBMISimple(70, 1.75, 'id');

calculateBMIImperial(weightInLbs: number, heightInFeet: number, heightInInches?: number, locale?: Locale): BMIResult

Calculates BMI using Imperial units (pounds and feet/inches).

import { calculateBMIImperial } from '@dodysat/bmi';

// 5 feet 9 inches, 154 pounds
const result = calculateBMIImperial(154, 5, 9);
const resultId = calculateBMIImperial(154, 5, 9, 'id');

Utility Functions

cmToMeters(heightInCm: number): number

Converts height from centimeters to meters.

import { cmToMeters } from '@dodysat/bmi';

const heightInMeters = cmToMeters(175); // 1.75

lbsToKg(weightInLbs: number, locale?: Locale): number

Converts weight from pounds to kilograms.

import { lbsToKg } from '@dodysat/bmi';

const weightInKg = lbsToKg(154.32); // 70

Localization Functions

getLocale(locale: Locale): LocaleData

Gets locale data for the specified language.

import { getLocale } from '@dodysat/bmi';

const enLocale = getLocale('en');
const idLocale = getLocale('id');

getSupportedLocales(): Locale[]

Gets all supported locale codes.

import { getSupportedLocales } from '@dodysat/bmi';

const locales = getSupportedLocales(); // ['en', 'id']

isLocaleSupported(locale: string): locale is Locale

Checks if a locale is supported.

import { isLocaleSupported } from '@dodysat/bmi';

if (isLocaleSupported('en')) {
  // English is supported
}

Types and Enums

BMICategory

enum BMICategory {
  UNDERWEIGHT = 'underweight',
  NORMAL_WEIGHT = 'normal_weight',
  OVERWEIGHT = 'overweight',
  OBESE_CLASS_I = 'obese_class_i',
  OBESE_CLASS_II = 'obese_class_ii',
  OBESE_CLASS_III = 'obese_class_iii'
}

BMIResult

interface BMIResult {
  bmi: number;                    // Calculated BMI value
  category: BMICategory;          // WHO BMI category
  categoryName: string;           // Human-readable category name
  range: string;                  // BMI range for the category
  recommendations: string[];      // Health recommendations
}

Locale and LocaleData

type Locale = 'en' | 'id';

interface LocaleData {
  categories: {
    underweight: { name: string; range: string; recommendations: string[] };
    normal_weight: { name: string; range: string; recommendations: string[] };
    overweight: { name: string; range: string; recommendations: string[] };
    obese_class_i: { name: string; range: string; recommendations: string[] };
    obese_class_ii: { name: string; range: string; recommendations: string[] };
    obese_class_iii: { name: string; range: string; recommendations: string[] };
  };
  errors: {
    weight_positive: string;
    height_positive: string;
    height_unrealistic: string;
    weight_unrealistic: string;
    cm_positive: string;
    lbs_positive: string;
  };
  units: {
    kg: string;
    m: string;
    cm: string;
    lbs: string;
    feet: string;
    inches: string;
  };
}

WHO BMI Categories

This library follows the World Health Organization (WHO) BMI classification system:

| Category | BMI Range | Description | |----------|-----------|-------------| | Underweight | < 18.5 | Below healthy weight range | | Normal Weight | 18.5 - 24.9 | Healthy weight range | | Overweight | 25.0 - 29.9 | Above healthy weight range | | Obese Class I | 30.0 - 34.9 | Moderate obesity | | Obese Class II | 35.0 - 39.9 | Severe obesity | | Obese Class III | ≥ 40.0 | Very severe obesity |

Usage Examples

Basic BMI Calculation

import { calculateBMI } from '@dodysat/bmi';

const result = calculateBMI({ weight: 70, height: 1.75 });

console.log(`Your BMI is: ${result.bmi}`);
console.log(`Category: ${result.categoryName}`);
console.log(`Range: ${result.range}`);
console.log('Recommendations:');
result.recommendations.forEach(rec => console.log(`- ${rec}`));

Using Imperial Units

import { calculateBMIImperial } from '@dodysat/bmi';

// Calculate BMI for someone who is 5'9" and 154 lbs
const result = calculateBMIImperial(154, 5, 9);

console.log(`BMI: ${result.bmi}`); // ~22.75
console.log(`Category: ${result.categoryName}`); // "Normal Weight"

Unit Conversions

import { calculateBMI, cmToMeters, lbsToKg } from '@dodysat/bmi';

// Convert from cm and lbs to metric
const heightInMeters = cmToMeters(175); // 1.75
const weightInKg = lbsToKg(154.32); // 70

const result = calculateBMI({ weight: weightInKg, height: heightInMeters });

Localization

The library supports multiple languages. Currently supported: English (en) and Indonesian (id).

import { calculateBMI, getSupportedLocales } from '@dodysat/bmi';

// Check supported locales
const locales = getSupportedLocales(); // ['en', 'id']

// Calculate BMI in English (default)
const resultEn = calculateBMI({ weight: 70, height: 1.75, locale: 'en' });
console.log(resultEn.categoryName); // "Normal Weight"

// Calculate BMI in Indonesian
const resultId = calculateBMI({ weight: 70, height: 1.75, locale: 'id' });
console.log(resultId.categoryName); // "Berat Badan Normal"

// Error messages are also localized
try {
  calculateBMI({ weight: -70, height: 1.75, locale: 'id' });
} catch (error) {
  console.log(error.message); // "Berat badan harus berupa angka positif dalam kilogram"
}

Error Handling

import { calculateBMI } from '@dodysat/bmi';

try {
  const result = calculateBMI({ weight: 70, height: 1.75 });
  console.log(`BMI: ${result.bmi}`);
} catch (error) {
  console.error('BMI calculation error:', error.message);
}

Error Messages

The library provides clear error messages for invalid inputs in multiple languages:

English

• "Weight must be a positive number in kilograms"
• "Height must be a positive number in meters"
• "Height seems unusually high. Please ensure height is in meters, not centimeters"
• "Weight seems unusually high. Please ensure weight is in kilograms"

Indonesian

• "Berat badan harus berupa angka positif dalam kilogram"
• "Tinggi badan harus berupa angka positif dalam meter"
• "Tinggi badan tampak tidak realistis. Pastikan tinggi dalam meter, bukan sentimeter"
• "Berat badan tampak tidak realistis. Pastikan berat dalam kilogram"

Development

Building the Library

npm run build

Running Tests

npm test

Running Tests in Watch Mode

npm run test:watch

Contributing

1. Fork the repository
2. Create a feature branch
3. Make your changes
4. Add tests for new functionality
5. Run the test suite
6. Submit a pull request

License

MIT License - see LICENSE file for details.

References

• WHO BMI Classification
• WHO Guidelines for BMI

Support

If you encounter any issues or have questions, please open an issue on GitHub.