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• You have to create a program that will handle when the register does not have enough cash or will have no cash after the transaction. Other than that it needs to return an array of the change in the form of an array, so that will be a 2D array.

• Data Structure Arrays

• It is easier to handle if you have to close the register, or if you know how much money is in your register beforehand and you will not have enough money to complete the transaction. For this it is recommended to have a function to assign this information to a variable.

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• Life is easier when you get to know the value of each currency type in the register instead of how much money is composed of that particular currency. So be sure to watch out for that.

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• You will have to get as much change from one type before moving to the next from greater value to lesser, and keep going until you have covered the whole change.

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Solution ahead!

// Create an object which hold the denominations and their values
var denom = [
  { name: 'ONE HUNDRED', val: 100.00},
  { name: 'TWENTY', val: 20.00},
  { name: 'TEN', val: 10.00},
  { name: 'FIVE', val: 5.00},
  { name: 'ONE', val: 1.00},
  { name: 'QUARTER', val: 0.25},
  { name: 'DIME', val: 0.10},
  { name: 'NICKEL', val: 0.05},
  { name: 'PENNY', val: 0.01}
];

function checkCashRegister(price, cash, cid) {
  var change = cash - price;

  // Transform CID array into drawer object
  var register = cid.reduce(function(acc, curr) {
    acc.total += curr[1];
    acc[curr[0]] = curr[1];
    return acc;
  }, {total: 0});

  // Handle exact change
  if (register.total === change) {
    return 'Closed';
  }

  // Handle obvious insufficent funds
  if (register.total < change) {
    return 'Insufficient Funds';
  }

  // Loop through the denomination array
  var change_arr = denom.reduce(function(acc, curr) {
    var value = 0;
    // While there is still money of this type in the drawer
    // And while the denomination is larger than the change reminaing
    while (register[curr.name] > 0 && change >= curr.val) {
      change -= curr.val;
      register[curr.name] -= curr.val;
      value += curr.val;

      // Round change to the nearest hundreth deals with precision errors
      change = Math.round(change * 100) / 100;
    }
    // Add this denomination to the output only if any was used.
    if (value > 0) {
        acc.push([ curr.name, value ]);
    }
    return acc; // Return the current Change Array
  }, []); // Initial value of empty array for reduce

  // If there are no elements in change_arr or we have leftover change, return
  // the string "Insufficient Funds"
  if (change_arr.length < 1 || change > 0) {
    return "Insufficient Funds";
  }

  // Here is your change, ma'am.
  return change_arr;
}

// test here
checkCashRegister(19.50, 20.00, [["PENNY", 1.01], ["NICKEL", 2.05], ["DIME", 3.10], ["QUARTER", 4.25], ["ONE", 90.00], ["FIVE", 55.00], ["TEN", 20.00], ["TWENTY", 60.00], ["ONE HUNDRED", 100.00]]);

🚀 Run Code

First, the CID array is transformed into a drawer object. Then we handle the conditions of exact change and insufficient funds. Then we loop through the denomination array and update the change and values while there is still money of this type in the drawer and while the denomination is larger than the change reminaing. Then we add this denomination to the output only if any was used. Finally, if there are no elements in change_arr or we have leftover change, return the string "Insufficient Funds".

• JS Array Reduce
• JS Reduce Made Easy
• JS Loops
• JS Array Push

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Thanks @Rafase282 @SaintPeter @erictleung for your help with Algorithm: Exact Change

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