How to iterate array while splicing

Question

I have an array INTERVALS and I want to remove a subset of elements from this array. I tried using for loop and splice, but it is not working as desired. It seems the for loop should not modify the array. Any help?

function remove_intervals(list) {
  for(i=0; i < INTERVALS.length; i++) {
    var o = INTERVALS[i];
    if(o in list) {
      clearInterval(o);
      INTERVALS.splice(i,1);
    }
  }
}

It is typically an anti-pattern to iterate over an array that you are modifying inside the iteration — Taplar
– Taplar, Commented May 19, 2020 at 22:31
Ah looks the indexing is somehow the issue.. Any alternative? @Taplar — across
– across, Commented May 19, 2020 at 22:33
Consider a usage of filter. Or consider iterating backwards, from the end to the beginning. — Taplar
– Taplar, Commented May 19, 2020 at 22:34
Oh iterating backwards doesn't disturb the indexing for splice. You're truely awesome! Thank you:) @Taplar — across
– across, Commented May 19, 2020 at 22:37
Iterating backwards does change the index, but not in a manner that you care, as it does not change the preceeding index that you will continue to process on. The index after that point will change, but you don't care. You've already processed past them — Taplar
– Taplar, Commented May 19, 2020 at 22:39

Robo Robok · Accepted Answer · 2020-05-19 22:39:20Z

2

You can use Array.prototype.filter like this:

function remove_intervals(list) {
    INTERVALS = INTERVALS.filter(id => {
        if (id in list) {
            clearInterval(id);
            return false;
        }

        return true;
    });
}

answered May 19, 2020 at 22:39

Robo Robok

23.1k22 gold badges85 silver badges146 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

marno11 · Accepted Answer · 2020-05-19 22:41:21Z

1

Could you do this using a the filter and inccludes methods to create a new array

const words = ['spray', 'limit', 'elite', 'exuberant', 'destruction', 'present'];
const toRemove = ['limit', 'elite', 'destruction'];

const result = words.filter(word => toRemove.includes(word));

console.log(result);
// expected output: Array ['spray', 'exuberant', 'present'];

answered May 19, 2020 at 22:41

marno11

5711 gold badge5 silver badges13 bronze badges

2 Comments

Robo Robok Over a year ago

Also, in operator looks for the property name, not for a value in an array.

marno11 Over a year ago

Ah, I see what you're trying to do now

Collectives™ on Stack Overflow

How to iterate array while splicing

2 Answers 2

Comments

2 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

2 Comments

Your Answer

Sign up or log in

Post as a guest

Related