Iterating over an array with "holes" in JavaScript - Stack Overflow

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I have got an array from which some items are going to be removed; but some loops are still running on them, so I want to simply skip the places where I remove my objects

I know that the syntax for(i in array) should do this because it iterates on the index, but how should I remove my items then ? Because when i do array[4] = null, my for just doesn't care and goes on trying to use the value at 4.

I also tried to check if !null but without success... thank you

I have got an array from which some items are going to be removed; but some loops are still running on them, so I want to simply skip the places where I remove my objects

I know that the syntax for(i in array) should do this because it iterates on the index, but how should I remove my items then ? Because when i do array[4] = null, my for just doesn't care and goes on trying to use the value at 4.

I also tried to check if !null but without success... thank you

• javascript
• arrays
• foreach
• iteration

Share Improve this question Follow asked Dec 12, 2012 at 20:09 RayjaxRayjax 7,7841313 gold badges5757 silver badges8585 bronze badges 3

• for in's are for enumerating object properties. You should be using a standard for loop for iterating over an array. For more info see stackoverflow./questions/5263847/… – Matt Commented Dec 12, 2012 at 20:11
• 2 If you really need to iterate over a sparse array, use for(i in array) { if(!isNaN(+i)) ... }. (Bonus tip: you probably don't need to iterate over a sparse array. This is only for cases in which you have a array with hugely distant indices, e.g. 5 and 10000000 are the only populated indices.) – apsillers Commented Dec 12, 2012 at 20:13
• Delete the array element properly: stackoverflow./questions/500606/…. – Felix Kling Commented Dec 12, 2012 at 20:39

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1 Answer 1

Sorted by: Reset to default 6

If you want to remove an item without leaving a hole, you should use .splice()

myarray.splice(idx, 1);

---

But if you're saying that you want the holes there, but want to skip them, then you can use delete to remove the item (leaving a hole), and use .forEach() for the iteration, which skips holes.

delete myarray[idx];

// ...

myarray.forEach(function(item, i) {
    // holes will be skipped
});

To support older browsers like IE8 and lower, you'll need to add a patibility patch for forEach().

• MDN .forEach() (Ignore the shorter patch. It's a poor non-pliant version.)

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