Rounding number off by 0.01

JavaScript
#1

I’m doing the last javascript project, but got in trouble with floating point number, I tried to fix it with .toFixed(2) but it still is, off by 0.01.

Here is the code

function checkCashRegister(price, cash, cid) {
  //check total cash in draw
  const totalCID = () => {
    let acc = 0;
    cid.forEach(each => acc += each[1])
    return Number(acc.toFixed(2));
  };
  //console.log(totalCID())

  //check change amount
  let changeDue = cash - price;

  //determine status
  const checkStatus = () => {
    return changeDue > totalCID()
    ? "INSUFFICIENT_FUNDS"
    : changeDue < totalCID()
    ? "OPEN"
    : "CLOSED"
  };

  //making an array/object to store our change
  let change = []; //for storing numbers according to bill/coin
  let changeReturn = []

  //making arrays that help determine which bill and coins we will use for the the change
  const changeCount = [100, 20, 10, 5, 1, 0.25, 0.10, 0.05, 0.01];
  let cashInDraw = cid.reverse();

  //making change return system
  for (let i = 0; i < changeCount.length; i++){
    while (changeDue >= changeCount[i]){
      if (cashInDraw[i][1] < changeCount[i]){
        break;
      };
      change.push(changeCount[i])
      changeDue -= changeCount[i];
      cashInDraw[i][1] -= changeCount[i];

    }
    //push change(bill/coins) and its value accordingly
    if (change.length !== 0){
      let acc = 0
      change.forEach(each => acc += each)
      changeReturn.push([cashInDraw[i][0], Number(acc.toFixed(2))]);
      change = [];
    }
  }
  //console.log(changeReturn)
  //assemple our check that include status and change
  let check = {}
  check.status = checkStatus();
  check.change = changeReturn;
  //console.log(check);
  //console.log(cashInDraw)

  return check;
}

checkCashRegister(3.26, 100, [["PENNY", 1.01], ["NICKEL", 2.05], ["DIME", 3.1], ["QUARTER", 4.25], ["ONE", 90], ["FIVE", 55], ["TEN", 20], ["TWENTY", 60], ["ONE HUNDRED", 100]])

Here is the Output:

{ status: 'OPEN',
  change: 
   [ [ 'TWENTY', 60 ],
     [ 'TEN', 20 ],
     [ 'FIVE', 15 ],
     [ 'ONE', 1 ],
     [ 'QUARTER', 0.5 ],
     [ 'DIME', 0.2 ],
     [ 'PENNY', 0.03 ] ] }

Notice the PENNY is paired with 0.03, but it should be 0.04.

So, what can I do to fix this problem. Any suggests will be appreciate, Thanks you.

#2

Hey there,

This is known as a floating point issue and a lot of people run in to it.

My recommendation is to convert everything into pennies first, before doing the math, then convert it back before returning.

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#3

the rounding issue is present every time you make an operation between decimal numbers, there are various places in your code in which you have such an operation but no check. I would suggest to follow @nhcarrigan suggestion

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