tvm-calculator/lib/index.js

A library of financial calculator functions allowing easy incorporation of time value of money calculations into any application

"use strict";

Object.defineProperty(exports, "__esModule", {
  value: true
});
exports["default"] = exports.calcInterestRate = exports.calcNPer = exports.calcPMT = exports.calcFV = exports.calcPV = void 0;

/* 
Basic financial formulas:
PV=Present Value. FV=Future value, PMT=payment per priod, NPer=Number of period,
IR=Annual interest rate, CF=Compound frequency, PF=payment frequency,
X=1 for beginning of period payment otherwise 0, i=effective interest

Financial equation: (General)
	(1): (PV+PMT(1+iX)/i)((1+i)^NPer-1)+PV + FV = 0
by using:
	(2): A=(1+i)^NPer-1
	(3): B=(1+iX)/i
you get:
	(4): (PV+PMT*B)*A+PV+FV=0
which solved for the other variable gives:
	(5): NPer=log((PMT*B-FV)/(PMT*B+PV))/log(1+i)
	(6): PV=-(FV+A*PMT*B)/(A+1)
	(7): PMT=-(FV+PV(A+1))/(A*B)
	(8): FV=-(PV+A(PV+PMT*B))
	(9): IR solved by iteration
Special case 1: IR=0 && PMT!=0; PV+PMT*NR+FV=0
	(10): FV=-(PV+NPer*PMT)
	(11): PV=-FV-NPer*PMT
	(12): PMT=-(FV+PV)/NPer
	(13): NPer=-(FV+PV)/PMT
Special case 2: IR!=0 && PMT=0
	(14): FV=-PV(1+A)
	(15): PV=-FV/(1+A)
	(16): NPer=log(-FV/PV)/log(1+i)
	(17): i=(FV/PV)^(1/NPer)-1  Condition PV*FV<0
*/
var calcRateEff = function calcRateEff(rate, isDiscrete, cf, pf) {
  if (isDiscrete) {
    return Math.pow(1 + rate / 100 / cf, cf / pf) - 1;
  }

  return Math.exp(rate / 100 / pf) - 1;
};

var calcRate = function calcRate(rateEff, isDiscrete, cf, pf) {
  if (isDiscrete) {
    return cf * (Math.pow(1 + rateEff, pf / cf) - 1) * 100;
  }

  return Math.log(Math.pow(1 + rateEff, pf)) * 100;
};

var calcVars = function calcVars(rate, nper, isBeginning, isDiscrete, cf, pf) {
  var rateEff = calcRateEff(rate, isDiscrete, cf, pf);
  var x = isBeginning ? 1 : 0;
  var a = Math.pow(1 + rateEff, nper) - 1;
  var b = (1 + rateEff * x) / rateEff;
  return {
    rateEff: rateEff,
    x: x,
    a: a,
    b: b
  };
};

var calcPV = function calcPV(params) {
  var rate = params.rate,
      nper = params.nper,
      pmt = params.pmt,
      fv = params.fv,
      _params$isBeginning = params.isBeginning,
      isBeginning = _params$isBeginning === void 0 ? false : _params$isBeginning,
      _params$isDiscrete = params.isDiscrete,
      isDiscrete = _params$isDiscrete === void 0 ? true : _params$isDiscrete,
      _params$cf = params.cf,
      cf = _params$cf === void 0 ? 12 : _params$cf,
      _params$pf = params.pf,
      pf = _params$pf === void 0 ? 12 : _params$pf;
  var vars = calcVars(rate, nper, isBeginning, isDiscrete, cf, pf);
  var rateEff = vars.rateEff,
      a = vars.a,
      b = vars.b;
  var pv;

  if (rateEff === 0) {
    pv = -1 * (fv - nper * pmt);
  } else if (pmt === 0) {
    pv = -1 * (fv / (a + 1));
  } else {
    pv = -1 * ((fv + a * pmt * b) / (a + 1));
  }

  return pv.toFixed(2);
};

exports.calcPV = calcPV;

var calcFV = function calcFV(params) {
  var rate = params.rate,
      nper = params.nper,
      pmt = params.pmt,
      pv = params.pv,
      _params$isBeginning2 = params.isBeginning,
      isBeginning = _params$isBeginning2 === void 0 ? false : _params$isBeginning2,
      _params$isDiscrete2 = params.isDiscrete,
      isDiscrete = _params$isDiscrete2 === void 0 ? true : _params$isDiscrete2,
      _params$cf2 = params.cf,
      cf = _params$cf2 === void 0 ? 12 : _params$cf2,
      _params$pf2 = params.pf,
      pf = _params$pf2 === void 0 ? 12 : _params$pf2;
  var vars = calcVars(rate, nper, isBeginning, isDiscrete, cf, pf);
  var rateEff = vars.rateEff,
      a = vars.a,
      b = vars.b;
  var fv;

  if (rateEff === 0) {
    fv = -1 * (pv - nper * pmt);
  } else if (pmt === 0) {
    fv = -1 * (pv * (1 + a));
  } else {
    fv = -1 * (pv + a * (pv + pmt * b));
  }

  return fv.toFixed(2);
};

exports.calcFV = calcFV;

var calcPMT = function calcPMT(params) {
  var rate = params.rate,
      nper = params.nper,
      pv = params.pv,
      fv = params.fv,
      _params$isBeginning3 = params.isBeginning,
      isBeginning = _params$isBeginning3 === void 0 ? false : _params$isBeginning3,
      _params$isDiscrete3 = params.isDiscrete,
      isDiscrete = _params$isDiscrete3 === void 0 ? true : _params$isDiscrete3,
      _params$cf3 = params.cf,
      cf = _params$cf3 === void 0 ? 12 : _params$cf3,
      _params$pf3 = params.pf,
      pf = _params$pf3 === void 0 ? 12 : _params$pf3;
  var vars = calcVars(rate, nper, isBeginning, isDiscrete, cf, pf);
  var rateEff = vars.rateEff,
      a = vars.a,
      b = vars.b;
  var pmt;

  if (rateEff === 0) {
    pmt = -1 * ((fv + pv) / nper);
  } else {
    pmt = -1 * ((fv + pv * (a + 1)) / (a * b));
  }

  return pmt.toFixed(2);
};

exports.calcPMT = calcPMT;

var calcNPer = function calcNPer(params) {
  var rate = params.rate,
      pmt = params.pmt,
      pv = params.pv,
      fv = params.fv,
      _params$isBeginning4 = params.isBeginning,
      isBeginning = _params$isBeginning4 === void 0 ? false : _params$isBeginning4,
      _params$isDiscrete4 = params.isDiscrete,
      isDiscrete = _params$isDiscrete4 === void 0 ? true : _params$isDiscrete4,
      _params$cf4 = params.cf,
      cf = _params$cf4 === void 0 ? 12 : _params$cf4,
      _params$pf4 = params.pf,
      pf = _params$pf4 === void 0 ? 12 : _params$pf4;
  var vars = calcVars(rate, 0, isBeginning, isDiscrete, cf, pf);
  var rateEff = vars.rateEff,
      b = vars.b;
  var nper;

  if (rateEff === 0) {
    nper = -1 * ((fv + pv) / pmt);
  } else if (pmt === 0) {
    nper = Math.log(-1 * (fv / pv)) / Math.log(1 + rateEff);
  } else {
    var t = pv + pmt * b;

    if (t !== 0) {
      t = (-1 * fv + pmt * b) / t;
    }

    if (t !== 0) {
      nper = Math.log(t) / Math.log(1 + rateEff);
    }
  }

  return nper.toFixed(2);
};
/*
	(1): (PV+PMT(1+iX)/i)((1+i)^NPer-1)+PV + FV = 0
	by using:
	(2): A=(1+i)^NPer-1
	(3): B=(1+iX)/i
	you get:
	(4): (PV+PMT*B)*A+PV+FV=0
*/


exports.calcNPer = calcNPer;

var iNewton3 = function iNewton3(nper, pmt, pv, fv, isBeginning, isDiscrete, cf, pf) {
  var fx = function fx(i, x) {
    return Math.pow(1 + i, nper) * pmt * (1 + x * i) - pmt * (1 + x * i) + fv * i + pv * i * Math.pow(1 + i, nper);
  };

  var f1x = function f1x(i, x) {
    var t = 1 + x * i;
    return (Math.pow(1 + i, nper) - 1) * (-1 * (pmt * t)) + nper * i * Math.pow(1 + i, nper - 1) * (pmt * t + pv * i);
  };
  /*
  const payment = (i, x) => {
  	const a = Math.pow(1 + i, nper) - 1;
  	const b = (1 + i * x) / i;
  	return -1 * ((fv + pv * (a + 1)) / (a * b));
  };
  */


  var period = function period(i, x) {
    if (i === 0) {
      return -1 * ((pv + fv) / pmt);
    }

    var b = (1 + i * x) / i;
    return Math.log((-1 * fv + pmt * b) / (pv + pmt * b)) / Math.log(1 + i);
  };

  var rateEff;
  var a; // Check for i === 0 is a solution and return

  if ((pv + nper * pmt + fv).toFixed(4) === 0) {
    return 0;
  }

  if (pmt * fv <= 0) {
    rateEff = Math.abs((nper * pmt + pv - fv) / (nper * pv));
  } else if (pmt * fv > 0) {
    if (pv !== 0) {
      a = -1;
    } else {
      a = 1;
    }

    rateEff = Math.abs(-1 * (fv + a * nper * pmt) / (3 * (pmt * Math.pow(nper - 1, 2) + pv + fv)));
  } else if (pv * pmt < 0) {
    rateEff = Math.abs((nper * pmt - fv + pv) / (nper * pv));
  } else {
    a = Math.abs(pmt / (Math.abs(pv) + Math.abs(-1 * fv)));
    rateEff = a + 1.0 / (a * nper * nper * nper);
  }

  var x = isBeginning ? 1 : 0;
  var np0 = period(0, x);
  var direction = 1;

  if (np0 < nper) {
    // Positive interest
    direction = 1;
  }

  if (np0 > nper) {
    // Negative interest
    direction = -1;
  }

  if (direction < 0 && rateEff > 0 || direction > 0 && rateEff < 0) {
    rateEff *= -1;
  }

  if (direction < 0 && rateEff < 0) {
    direction = 1;
    rateEff *= -1;
  }

  var iNew = rateEff;
  var iOld = rateEff;
  var iCalc = calcRate(rateEff, isDiscrete, cf, pf);
  var dx;
  var iCalcOld;
  var fi;
  var f1i;

  for (var count = 1; count <= 100; count += 1) {
    iOld = iNew;
    fi = fx(iOld, x);
    f1i = f1x(iOld, x);
    dx = iOld * (fi / f1i);
    iNew = iOld - dx;
    fi = fx(iNew, x);
    iCalc = calcRate(iNew, isDiscrete, cf, pf);
    iCalcOld = calcRate(iOld, isDiscrete, cf, pf);

    if (iCalc.toFixed(4) === iCalcOld.toFixed(4)) {
      break;
    }
  } // rateEff = iNew;


  return iNew;
};

var calcInterestRate = function calcInterestRate(params) {
  var nper = params.nper,
      pmt = params.pmt,
      pv = params.pv,
      fv = params.fv,
      _params$isBeginning5 = params.isBeginning,
      isBeginning = _params$isBeginning5 === void 0 ? false : _params$isBeginning5,
      _params$isDiscrete5 = params.isDiscrete,
      isDiscrete = _params$isDiscrete5 === void 0 ? true : _params$isDiscrete5,
      _params$cf5 = params.cf,
      cf = _params$cf5 === void 0 ? 12 : _params$cf5,
      _params$pf5 = params.pf,
      pf = _params$pf5 === void 0 ? 12 : _params$pf5;
  var rate;

  if (pmt === 0) {
    rate = Math.pow(-1 * (fv / pv), 1 / nper) - 1;
  } else {
    var i = iNewton3(nper, pmt, pv, fv, isBeginning, isDiscrete, cf, pf);
    rate = calcRate(i, isDiscrete, cf, pf) / 100;
  }

  rate *= 100;
  return rate.toFixed(2);
};

exports.calcInterestRate = calcInterestRate;
var tvmCalculator = {
  calcNPer: calcNPer,
  calcInterestRate: calcInterestRate,
  calcPV: calcPV,
  calcPMT: calcPMT,
  calcFV: calcFV
};
var _default = tvmCalculator;
exports["default"] = _default;