Why does my while loop condition not end the loop?

Question

I am confused as to why my function continues to loop. wedgesNeeded = number, limes = array

function limesToCut(wedgesNeeded, limes) {
  let total = 0
  while (wedgesNeeded > 0) {
    let lime = limes.shift()
    switch (lime) {
      case 'small':
        wedgesNeeded -= 6;
        total++;
        break;
      case 'medium':
        wedgesNeeded -= 8;
        total++;
        break;
      default:
    }
  }
  return total
}
console.log(limesToCut(12, ['small','small']));

Please include a minimal reproducible example, with enough code that we can reproduce the situation. — Heretic Monkey
– Heretic Monkey, Commented Aug 18, 2022 at 18:18
Are you sure that lime has any of the values in the switch? If you put an alert in the default case, does that appear? — Andrew Morton
– Andrew Morton, Commented Aug 18, 2022 at 18:18
Note that if limes contains none of those strings, it will loop indefinitely. Also, if limes does not contain enough of those string to get wedgesNeeded down to 0, it will continue to loop. — Heretic Monkey
– Heretic Monkey, Commented Aug 18, 2022 at 18:19
@HereticMonkey - I thought the same at first, but if it's default doesn't it move to the next lime? let lime = limes.shift(); it only gets evaluated once, right? I have no idea why this would loop infinitely; I'd think you'd eventually run out of limes. — Chuck
– Chuck, Commented Aug 18, 2022 at 18:20
@AndrewMorton yeah the values are correct. If I console.log(${wedgesNeeded} ${total}) after the switch it will return all the correct values. The total increases correctly and the wedgesNeeded will decrease correctly. — Conrade
– Conrade, Commented Aug 18, 2022 at 18:22

realSamy · Accepted Answer · 2022-08-18 18:37:36Z

1

Your situation occurs when the wedgesNeeded is much bigger than what you expect; Your loop will empty the limes array but wedgesNeeded is still bigger than 0

function limesToCut(wedgesNeeded, limes) {
  let total = 0
  while (wedgesNeeded > 0 && !!limes.length) {
    let lime = limes.shift()
        switch (lime) {
          case 'small':
            wedgesNeeded -= 6;
            total++;
            break;
          case 'medium':  
            wedgesNeeded -= 8;
            total++;
            break;
          default:
        }
    }
  return total
}

count = limesToCut(200000, ['small', 'medium', 'small', 'medium', 'small', 'medium'])
console.log(count)

Edit: Replaced the if condition by while condition!

edited Aug 18, 2022 at 18:37

answered Aug 18, 2022 at 18:27

realSamy

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4 Comments

Conrade Over a year ago

This works, thank you. Is there a way to remove the if statement and include another condition in the whileloop instead?

realSamy Over a year ago

@Conrade sure, done!

Conrade Over a year ago

Legend, mate. What does the '!!' mean?

realSamy Over a year ago

What is the !! (not not) operator in JavaScript @Conrade

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