Booleans as flags in loops

1

Is it a bad practice to use booleans as flags? I’ve been using this pattern for a couple of the intermediate algorithms and something tells me there’s better ways.

for (i=0; i < 2000; i ++) {
brokenPart = false;

    for (loop criteria) {

      if (part is broken){
        brokenPart = true;
        break;
      }
      
    }
    if (brokenPart) {
      throw out part.
    }
    
}
2

When you find yourself starting to do something like this, it might be time to consider using a while loop.

3 Likes
3

It depends, a while loop may end up just as ugly, since you’ll be manually incrementing the second index.

4

But why do you even need a flag there, what is wrong with this?

for (i=0; i < 2000; i ++) {
    for (loop criteria) {
        if (part is broken) {
            throw out part.
            break;
        }
    }
}
5

Maybe I’m missing something, but why aren’t the two if statements combined and get rid of brokenPart?

for (i=0; i < 2000; i ++) {
  for (loop criteria) {
    if (part is broken){
      throw out part.
      break;
    }
  } 
}
6

LOL, lynx beat me to it while I was typing. :slight_smile:

1 Like
7

Hi,

Ah I think this might help with my question then. I’ve added the code after the inner for loop as an example of what I’m trying to do.

for (i=0; i < 2000; i ++) {
    for (loop criteria) {
        if (part is broken) {
            throw out part.
            break;
        }
    } if (part passed all testes) {
           put the part into the bin. ( array.push(part) )
       }
}
8

What does “throw out” mean? If it just means it is still in the object or array, “part passed all tests” could just be a membership check (is it still in?).

9

Throw out is to do nothing with the part. Skip it.

10

Then a flag is fine. If you wanted to avoid it, you could add all the parts to the bin first and remove the broken ones from there instead.

1 Like
11

Thanks everyone for all the insights. :beers:
I’ll try all the ideas out in the rest of the challenges and rewrite some of my finished ones.

13

Any good books, resources, on how to make code more efficient and/or elegant or when to use x vs y when coding?

14

I’m sure there are some good books out there, but I think a lot of this just comes with experience. After a while, you get a “Spidey Sense” for these things. In order to write good code, you’ve got to write a lot of bad code first.

1 Like
15

Check this SO question, I’m not sure it’s better style but will give you another option.

https://www.google.de/url?sa=t&source=web&rct=j&url=https://stackoverflow.com/questions/1564818/how-to-break-nested-loops-in-javascript/1564838&ved=2ahUKEwjhraXPjrTZAhUIOBQKHXolA5AQFjABegQIXxAB&usg=AOvVaw0pb-wHJ2lB-HUByYZfMCdT

1 Like
16

A simpler and more functional/declarative style:

parts.forEach(part => {
  if (part.status === 'broken') {
    part.throwOut();
  }
});

Using JavaScript’s native array methods, you can also do things like filtering the parts by status:

const brokenParts = parts.filter(part => part.status === 'broken');
// a new array of all the broken parts

Or checking if any of the parts are broken:

const somePartsBroken = parts.some(part => part.status === 'broken');
// true if 1 or more are broken; false if 0 are broken
2 Likes
17

:bulb: Wasn’t aware of forEach() and some(). Definitely seeing the the usefulness and possibilities from your examples. Thank you for that. Much more reading to do.

18

Thanks again everyone. :beers::beers:

Before posting this topic I was stuck on the Sum All Primes challenge for a couple of days. It was definitely a brain buster. I finished it (the code is a bit verbose) then posted this topic. Your answers have directly helped me finish the next five challenges. Definitely made use of more while loops and forEach().