Potential issues for recursive function not being called in another function

Question

I'm trying to build a cash register (an algorithm project in FreeCodeCamp) and I've created a function (giveChange(), a recursive function) to be invoked in another separate function (checkCashRegister).

However, the function is not being called. I would like function checkCashRegister to return 0 in my case.

I checked whether it's the problem of placing "return" in the wrong place in for loop or problems of scope. Doesn't seem either.

function giveChange(diff, cid) {       
  for(let i = cid.length - 1; i > 0; i--) {
    if(cid[i-1][0] <= diff && diff <= cid[i][0]) {
      diff = diff - Math.min(cid[i-1][1], cid[i-1][0]*Math.ceil(((diff-cid[i-1][0])/cid[i-1][0])))
      if(diff !== 0) {
        giveChange(diff, cid)
      } else {
        return diff
      }
    }
  }
  return diff
}

function checkCashRegister(price, cash, cid) {
 
  let diff = cash - price
  cid[0][0] = 0.01
  cid[1][0] = 0.05
  cid[2][0] = 0.1
  cid[3][0] = 0.25
  cid[4][0] = 1
  cid[5][0] = 5
  cid[6][0] = 10
  cid[7][0] = 20
  cid[8][0] = 100

  giveChange(diff, cid)

  return diff
}

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]])

In both `giveChange(diff, cid)` calls you ignore the return value. You appear to assume that `diff = diff - Math.min(cid[i-1][1], cid[i-1][0]*Math.ceil(((diff-cid[i-1][0])/cid[i-1][0])))` is assigning to some _outer_ `diff`. That’s not how JavaScript works. See [Recursive function returns undefined](/q/12737970/4642212) and [Is JavaScript a pass-by-reference or pass-by-value language?](/q/518000/4642212). — Sebastian Simon, Mar 22 '22 at 15:50
`giveChange(diff, cid)` does not modify the variable `diff`, it returns a new value which you aren't capturing. Also, inside giveChange, you return stuff in a few places but not when (diff !== 0) - `return giveChange(diff, cid)` probably. — James, Mar 22 '22 at 15:50

dippas · Accepted Answer · 2022-03-22T16:05:34.523

You are missing return keyword before invoking givechange(diff, cid),

Note: I've updated the condition and used a ternary to not repeat the return keyword

function giveChange(diff, cid) {
  for (let i = cid.length - 1; i > 0; i--) {
    if (cid[i - 1][0] <= diff && diff <= cid[i][0]) {
      diff = diff - Math.min(cid[i - 1][1], cid[i - 1][0] * Math.ceil(((diff - cid[i - 1][0]) / cid[i - 1][0])))
      return diff !== 0 ? giveChange(diff, cid) : diff
    }
  }
  console.log(diff)
  return diff
}

function checkCashRegister(price, cash, cid) {

  let diff = cash - price
  cid[0][0] = 0.01
  cid[1][0] = 0.05
  cid[2][0] = 0.1
  cid[3][0] = 0.25
  cid[4][0] = 1
  cid[5][0] = 5
  cid[6][0] = 10
  cid[7][0] = 20
  cid[8][0] = 100

  return giveChange(diff, cid)
}

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]
])

Potential issues for recursive function not being called in another function

1 Answers1