cbe-amortization-table/cbe-amortization-table.js

Normal amortization as well as NPV for CBE

/*
 * cbe-amortization-table
 * Calculating CBE's Amortization
 * https://github.com/gama1221/cbe-amortization-table
 *
 * Copyright (c) 2023 Getinet Amare Mekonnen
 * Licensed under the CBE license.
 */

/**
 *
 * @param {number} num - An input to be rounded
 * @returns - It returns two decimal point rounded value
 */
const roundTheValue = (num) => {
    return Math.round(num * 100) / 100;
  };
  /**
   *
   * @param {number} amount - Original Loan
   * @param {number} annualInterestRate - Annual interest rate to be paid for loan
   * @param {number} loanPeriodInYears - Length of a year that a loan takes to complete
   * @param {number} numberOfPaymentsPerYear - It holds how many number of years it tooks to complete the loan
   * @param {number} principalSum - Summation of each principal for number of payments
   * @param {number} cumulativeInterest - Summation of interests.
   *
   *  @returns {{ principal: number, interest: number, scheduledPayment: number, endingBalance: number, cumulativeInterest: number }}
   */
  var getNextPaymentSchedule = (
    amount,
    annualInterestRate,
    loanPeriodInYears,
    numberOfPaymentsPerYear,
    principalSum,
    cumulativeInterest
  ) => {
    var principal;
    var interest;
    var scheduledPayment;
    var irmPow;
    var interestRateMonth = annualInterestRate / 100 / numberOfPaymentsPerYear;
    var numberOfPayment;
  
    numberOfPayment = loanPeriodInYears * numberOfPaymentsPerYear;
  
    irmPow = Math.pow(1 + interestRateMonth, -numberOfPayment);
    scheduledPayment = roundTheValue(
      (amount * (annualInterestRate / 100)) /
        (numberOfPaymentsPerYear * (1 - irmPow))
    );
    interest = roundTheValue((amount - principalSum) * interestRateMonth);
    principal = scheduledPayment - interest;
  
    return {
      principal: principal,
      interest: interest,
      scheduledPayment: scheduledPayment,
      endingBalance: amount - principalSum - principal,
      cumulativeInterest: cumulativeInterest + interest,
    };
  };
  
  /**
   * It holds the parametrs we provide on the GUI, It has four parametrs
   * @param {number} amount - Original Loan
   * @param {number} annualInterestRate - Annual interest rate to be paid for loan
   * @param {number} loanPeriodInYears - Length of a year that a loan takes to complete
   * @param {number} numberOfPaymentsPerYear - It holds how many number of years it tooks to complete the loan
   *
   * @returns {{ scheduledPayments: number, amount: number, cumulativeInterest: number, principalSum: number, sum: number }}
   */
  
  const CBEAmortization = (
    amount,
    annualInterestRate,
    loanPeriodInYears,
    riskPremium,
    // waiver,
    numberOfPaymentsPerYear
  ) => {
    if (
      !amount ||
      amount <= 0 ||
      !loanPeriodInYears ||
      loanPeriodInYears <= 0 ||
      !annualInterestRate ||
      annualInterestRate <= 0 ||
      !riskPremium ||
      riskPremium <= 0 
      
    ) {
      throw new Error(
        "wrong parameters: "
          .concat(amount, " ")
          .concat(loanPeriodInYears, " ")
          .concat(riskPremium, " ")
          .concat(annualInterestRate)
      );
    }
    var scheduledPayments = [];
    var cumulativeInterest = 0;
    var principalSum = 0;
    var sum = 0;
  
    var p_s = 0;
    var s_s = 0;
    var i_s = 0;
    var m = 0;
  
    var yearlyScheduledPayment = [];
    var yearlyPrincipalSummation = [];
    var yearlyInterestSummation = [];
    var NPV = [];
    for (var i = 0; i < loanPeriodInYears * numberOfPaymentsPerYear; i++) {
      var inst = getNextPaymentSchedule(
        amount, 
        annualInterestRate,
        loanPeriodInYears,
        numberOfPaymentsPerYear,
        principalSum,
        cumulativeInterest,
      );
      sum += inst.scheduledPayment;
      principalSum += inst.principal;
      cumulativeInterest += inst.interest;
      s_s += inst.scheduledPayment;
      p_s += inst.principal;
      i_s += inst.interest;
      // for()
      if (i === loanPeriodInYears * numberOfPaymentsPerYear - 1) {
        principalSum += inst.endingBalance;
        sum += inst.endingBalance;
        inst.endingBalance = 0;
      }
      if(m === (numberOfPaymentsPerYear - 1))  {
        yearlyScheduledPayment.push(s_s);
        yearlyPrincipalSummation.push(p_s);
        yearlyInterestSummation.push(i_s);
        s_s = 0;
        i_s = 0;
        p_s = 0;
        m = -1;
      }
      m++;
      scheduledPayments.push(inst);
      var riskPremiumWithAnnualInterestRate = (1+(parseFloat(annualInterestRate) + parseFloat(riskPremium))/100);
      if(i === (loanPeriodInYears * numberOfPaymentsPerYear - 1)){
        /**
         *  Let me sum the following values
         *    yearlyPrincipalSummation
         *    yearlyInterestSummations
         *  And compute the NPV
         */
        var power = 1;
        for(var n = 0;n < yearlyInterestSummation.length; n++){
          var npv1 = ((yearlyInterestSummation[n] + yearlyPrincipalSummation[n]) / Math.pow(riskPremiumWithAnnualInterestRate, power)); 
          NPV.push(npv1);
          npv1 = 0;
          power++; 
        }
        /**
         * Summation of NPV
         */
        var npmSummation = 0;
        for(var s = 0; s < NPV.length; s++){
          npmSummation += NPV[s];
        }
      }
    }
    return {
      scheduledPayments: scheduledPayments,
      amount: roundTheValue(amount),
      cumulativeInterest: roundTheValue(cumulativeInterest),
      principalSum: roundTheValue(principalSum),
      sum: roundTheValue(sum),
      scheduledPayment:inst.scheduledPayment,
      actualNumberOfPayments: (loanPeriodInYears * numberOfPaymentsPerYear),
      yearlyPrincipalSummation:yearlyPrincipalSummation,
      yearlyInterestSummation:yearlyInterestSummation,
      yearlyScheduledPayment:yearlyScheduledPayment,
      NPV:roundTheValue(npmSummation),
    };
  };
  module.exports = CBEAmortization;