Build a Cash Register Project - Random approval for test #13 and #19

JavaScript
1

Hi, after all the other test were approved, i noticed that the test #13 sometimes was checked and sometimes not, with the same code, i started spaming a little bit the “Run the test” and the code approved, #13 and #19 was done.
I’m curious why that happens. Here is the code:

let cid = [
  ['PENNY', 1.01],
  ['NICKEL', 2.05],
  ['DIME', 3.1],
  ['QUARTER', 4.25],
  ['ONE', 90],
  ['FIVE', 55],
  ['TEN', 20],
  ['TWENTY', 60],
  ['ONE HUNDRED', 100]
];

const divCid = document.getElementById("cid");
const inputCash = document.getElementById("cash");
const purchaseBtn = document.getElementById("purchase-btn");
const divChange = document.getElementById("change-due");
const pPrice = document.getElementById("price");
divCid.textContent = cid
const price = 19.5;
pPrice.textContent = `Price: $${price}`;

class Register {
  constructor(){
    this.amountWorthChange = [[0,0,0,0,0,0,0,0,0],[1,5,10,50,100,500,1000,2000,10000],[0,0,0,0,0,0,0,0,0]]
  };

 calculateAmount() {
   cid = cid.map((subArray) => [subArray[0],subArray[1]*100])

  this.amountWorthChange[0] = this.amountWorthChange[1].map((worth, i) => cid[i][1]/worth);
  }


  change() {
    return parseFloat(inputCash.value) - price;
  };

  calculateChangeDisponibility(){
    this.calculateAmount()
    let change = change()*100;
    for (let i = 8; i > -1; i--) {
      while(change >= this.amountWorthChange[1][i] && this.amountWorthChange[0][i] > 0) {
        change -= this.amountWorthChange[1][i];
        this.amountWorthChange[0][i] --;
        this.amountWorthChange[2][i] += this.amountWorthChange[1][i];
      };
    };
    return change
  };

  options() {

    const cidSum = cid.reduce((acc, subArray) => acc + subArray[1], 0);

    const changeDisponibility = !this.calculateChangeDisponibility();

    const cash = parseFloat(inputCash.value)

    if(price > cash) {
      alert("Customer does not have enough money to purchase the item")
    }

    else if(price === cash) {
      divChange.innerHTML = "No change due - customer paid with exact cash"
    }

    else if(cidSum === this.change() && price < cash && changeDisponibility && this.amountWorthChange[0].every(number => number===0)){
        this.updateClosedText()
        this.updateCid()
        divCid.textContent = cid
    }

    else if(cidSum > this.change() && price < cash && changeDisponibility){
       this.updateText()
       this.updateCid()
       divCid.textContent = cid
    }

    else if(!changeDisponibility){
      divChange.innerHTML = "Status: INSUFFICIENT_FUNDS"
    }
    this.resetAmountChangeArray() 
    inputCash.value = ""
    
  }

  resetAmountChangeArray() {
  this.amountWorthChange[2] = this.amountWorthChange[2].map(() => 0);
  this.amountWorthChange[0] = this.amountWorthChange[0].map(() => 0);

}

  updateText() {
    let text = "Status: OPEN"
    for (let i = 8; i > -1; i--) {
      if(this.amountWorthChange[2][i] > 0) {
        text += `</br>${cid[i][0]}: $${this.amountWorthChange[2][i]/100}`
      }
    }
    return divChange.innerHTML = text
  }

  updateClosedText() {
    let text = "Status: CLOSED"
    for (let i = 8; i > -1; i--) {
      if(this.amountWorthChange[2][i] > 0) {
        text += `</br>${cid[i][0]}: $${this.amountWorthChange[2][i]/100}`
      }
    }
    return divChange.innerHTML = text
  }

  updateCid() {
  cid = cid.map((subArray, i) => [subArray[0], (subArray[1] - this.amountWorthChange[2][i]) / 100]);
}

};

const register = new Register

purchaseBtn.addEventListener("click", () => register.options())
2

those two are random, if your code doesn’t pass them sometimes you probably have a floating point issue somewhere

how do you deal with the issue that operation with decimals are terribly unprecise?
0.1 + 0.2 results in 0.30000000000000004

multiplication and division is worse than that

3

I’m trying to identify every time a operation with decimals ocurrs and aply math.round(x*100)/100. In teory if i cover all the decimal operations i shouldn’t have any problem right?

4

you don’t need to do it at all operations, you can multiply by 100 as first thing, and divide by 100 as last thing before giving the output

5

Thanks! i’m done!, also i was using a worth of “$0.5” for quarter instead of “$0.25”.