@mtdevworks/toolkit

India-specific financial calculators & developer utilities — used by mtdevworks.com/tools

Install

npm install @mtdevworks/toolkit

Quick Start

import {
  calculateSip,
  formatJson,
  generatePassword,
} from '@mtdevworks/toolkit';

// SIP Investment Returns
const sip = calculateSip({
  monthlyAmount: 10000,
  years: 10,
  expectedReturn: 12,
});
console.log(sip.corpus); // ₹23,23,391
console.log(sip.cagr); // 12%

// Format JSON
const formatted = formatJson('{"b":2,"a":1}', { sortKeys: true, indent: 2 });

// Generate Secure Password
const [pw] = generatePassword({ length: 20, symbols: true });
console.log(pw.password); // "kQ#9xR!mP2..."
console.log(pw.strength); // "very-strong"

Sub-path Imports

Import only what you need for smaller bundles:

import { calculateEmi } from '@mtdevworks/toolkit/finance';
import { base64Encode } from '@mtdevworks/toolkit/dev';

Finance Calculators

calculateGstLateFee(input)

GST late filing fee + 18% interest for GSTR-3B, GSTR-1, GSTR-4, GSTR-9.

import { calculateGstLateFee } from '@mtdevworks/toolkit';

const result = calculateGstLateFee({
  returnType: '3B',
  isNil: false,
  daysLate: 45,
  taxLiability: 100000,
  annualTurnover: 10000000,
});
// { lateFee: 2000, interest: 2219.18, total: 4219.18, dailyFee: 50, capped: true }

calculateHra(input)

HRA exemption under Section 10(13A) — min of actual HRA, rent minus 10% basic, 50%/40% of basic.

const result = calculateHra({
  basicAnnual: 600000,
  hraReceived: 300000,
  rentPaidAnnual: 240000,
  isMetro: true,
});
// { exemption: 180000, taxableHra: 120000, ... }

calculateSip(input)

SIP returns with CAGR, inflation-adjusted corpus, and equity LTCG or debt tax.

| Field | Type | Description | | ---------------- | --------------------- | ------------------------------- | | monthlyAmount | number | Monthly SIP amount | | years | number | Investment period | | expectedReturn | number | Annual return % | | inflation | number? | Inflation rate % (default: 6) | | fundType | 'equity' \| 'debt'? | Tax treatment (default: equity) |

calculateEmi(input)

EMI with year-by-year amortization table and prepayment analysis.

const result = calculateEmi({
  principal: 5000000,
  rate: 8.5,
  tenureYears: 20,
  annualPrepayment: 100000,
});
console.log(result.emi); // 43391.22
console.log(result.actualTenureYears); // 15 (reduced by prepayment)
console.log(result.amortization); // [{ year, principalPaid, interestPaid, balance }]

calculateFd(input) / calculateRd(input)

Fixed Deposit and Recurring Deposit with quarterly compounding, TDS, and senior citizen bonus.

calculateIncomeTax(input)

Old vs New regime comparison for FY 2025-26 with all major deductions.

const result = calculateIncomeTax({
  grossIncome: 1500000,
  deductions80c: 150000,
  deductions80d: 25000,
  hraExemption: 180000,
});
// { oldRegime: { tax: ... }, newRegime: { tax: ... }, recommended: 'old', savings: 42000 }

calculateGratuity(input)

Gratuity under Payment of Gratuity Act — under/not-under Act formulas, ₹25L tax exemption cap.

optimizeSalary(input)

CTC-to-take-home breakdown with Old vs New regime comparison, EPF, HRA exemption.

Developer Utilities

formatJson(input, options?) / minifyJson(input) / validateJson(input)

formatJson('{"b":2,"a":1}', { sortKeys: true, indent: 4 });
minifyJson('{ "a" : 1 }'); // '{"a":1}'
validateJson('invalid'); // { valid: false, error: "..." }

base64Encode(input, options?) / base64Decode(input, options?)

base64Encode('Hello World'); // "SGVsbG8gV29ybGQ="
base64Encode('Hello World', { urlSafe: true }); // "SGVsbG8gV29ybGQ"
base64Decode('SGVsbG8gV29ybGQ='); // "Hello World"

generateHash(input, algorithms?)

Requires Node.js. Generates MD5, SHA-1, SHA-256, SHA-512 hashes.

const hashes = generateHash('my secret data');
// { md5: "...", sha1: "...", sha256: "...", sha512: "..." }

const sha = generateHash('my data', ['sha256']);
// { sha256: "..." }

generatePassword(options?)

Cryptographically secure password generation with entropy scoring.

const passwords = generatePassword({
  length: 24,
  uppercase: true,
  lowercase: true,
  digits: true,
  symbols: true,
  excludeAmbiguous: true,
  count: 5,
});
// [{ password: "...", entropy: 142.56, strength: "very-strong" }, ...]

Also Available As

| Channel | URL | | ------------- | ---------------------------------------------------- | | Web UI | mtdevworks.com/tools | | REST API | api.mtdevworks.com | | Portfolio | mtdevworks.com |

License

MIT © mtdevworks