Cash-register-project

JavaScript
1

Tell us what’s happening:
Hello, guys! My function is passing all test. But I started to think about 2nd condition (when status should be CLOSE). I wrote test in repl.it with one extra case: when price = 95, cash = 100 and cid has one 5$ for change. So which output should be in this case? This one:

{status: "CLOSED", change: [["FIVE", 5], ["NICKEL", 0], ["DIME", 0], ["QUARTER", 0], ["ONE", 0], ["PENNY", 0], ["TEN", 0], ["TWENTY", 0], ["ONE HUNDRED", 0]]}

Also why should I push all zero units in output? Could somebody explain me, please? Thanks.

P.S. I’ll be glad if somebody criticize my code.

Your code so far



const checkCashRegister = (price, cash, cid) => {
  const currencyTable = {
    0: 10, 1: 50, 2: 100, 3: 250, 4: 1000,
    5: 5000, 6: 10000, 7: 20000, 8: 100000,
  };
  
  let remainder = (cash - price) * 1000;
  
  const iter = (change, i) => {
    if (i === -1) return { ['status']: 'INSUFFICIENT_FUNDS', change: [] };
    const notesNum = Math.floor(remainder / currencyTable[i]),
          have = cid[i][1] * 1000,
          need = currencyTable[i] * notesNum,
          currNote = cid[i][0],
          currentChange = (have > need ? need : have);

    if (have === 0) {
      newChange = [[currNote, 0], ...change];
      return iter(newChange, i-1);
    } else if (notesNum === 0) return iter(change, i-1);

    remainder -= currentChange;
    newChange = [...change, [currNote, currentChange/1000]];
    
    if (remainder === 0) {
      newChange = newChange.sort((a, b) => a[1] < b[1]);
      const isClose = cidArr => cidArr.filter((unit, i) => unit[1] === newChange[i][1]).length > 0;

      const status = newChange.length < 9 ? 'OPEN' : isClose(cid) ? 'CLOSED' : 'OPEN';
      return { status, change: newChange };
    }
    
    return iter(newChange, i-1);
  };
  
  return iter([], 8);
};

// Example cash-in-drawer array:
// [["PENNY", 1.01],
// ["NICKEL", 2.05],
// ["DIME", 3.1],
// ["QUARTER", 4.25],
// ["ONE", 90],
// ["FIVE", 55],
// ["TEN", 20],
// ["TWENTY", 60],
// ["ONE HUNDRED", 100]]

checkCashRegister(19.5, 20, [["PENNY", 1.01], ["NICKEL", 2.05], ["DIME", 3.1], ["QUARTER", 4.25], ["ONE", 90], ["FIVE", 55], ["TEN", 20], ["TWENTY", 60], ["ONE HUNDRED", 100]]);

Your browser information:

User Agent is: Mozilla/5.0 (X11; Ubuntu; Linux i686; rv:59.0) Gecko/20100101 Firefox/59.0.

Link to the challenge:

2

The reason for the structure of the input and output (the cid/“change in drawer” parameter) is that you need a way to represent the actual cash register as an abstracted collection (structure)of information(data). The data structure returned is a cid object in the same format to make clear that every “slot” of the cash register drawer is explicitly represented, and as such, doesn’t need to be changed to feed it back into the same function again (or into another function which operates on a cid object.

3

If I get it right, you mean mutations here. So inputed cid shouldn’t be changed during function execution. Right? I understand it.

But in outputed object “change” key means change that we return to customer, not cid. And in other tests provided in this project this array (“change” key) never have units with 0 values. For example, here change will be only [QUARTER, 0.5], no zeros:

checkCashRegister(19.5, 20, [["PENNY", 1.01], ["NICKEL", 2.05], ["DIME", 3.1], ["QUARTER", 4.25], ["ONE", 90], ["FIVE", 55], ["TEN", 20], ["TWENTY", 60], ["ONE HUNDRED", 100]]) should return {status: "OPEN", change: [["QUARTER", 0.5]]}

And only in the last test change has actual change value + zeros: [[“PENNY”, 0.5], [“NICKEL”, 0], [“DIME”, 0], [“QUARTER”, 0], [“ONE”, 0], [“FIVE”, 0], [“TEN”, 0], [“TWENTY”, 0], [“ONE HUNDRED”, 0]] and I’m wondering why…

4

Oh, my bad. It’s been a while since I did this challenge. My answer is still similar: The issue is one of data structures. There are two possible reasons to design the output data structure as the challenge demands:

  1. For teaching purposes: Makes sure that the student is dealing with the fact that the other “slots” for possible currency denominations are being handled.

  2. For interoperability with other objects: Let’s say that you also have created a class Wallet that you will give that change back to. By forcing the data structure to include all the different slots, you can quickly merge them by using the Object.keys() method to return an array of the change object’s keys and iterating over the keys using foreach. There are ways to achieve this with partial objects, but by explicitly stating which values are zero, you can be assured that no data has been left out.

5

Hi,
I like your solution, but here’s where it fails:
console.log(checkCashRegister(19.7, 20, [[“PENNY”, 0], [“NICKEL”, 0], [“DIME”, 1], [“QUARTER”, 0], [“ONE”, 1], [“FIVE”, 0], [“TEN”, 0], [“TWENTY”, 0], [“ONE HUNDRED”, 0]]))

(20 - 19.7) * 1000 equals 300.0000000000007
Just want to help you make it perfect :slight_smile: