Deleting an element from an Array/Object in Javascript

I'm going to post that here because it's the second time I stumble upon this "problem" and the second time I lost some precious time to understand what was going on.

I had a Javascript Array, named elements and I wanted to remove one of its properties by its index i.

I know that merely calling elements[i] = null won't work (the property will still be present in the array and the length won't be updated.

Calling delete elements[i] won't work either. Same result.

I had to use elements.splice(i, 1) to effectively remove the element and update the length value.

Also note that sometimes I accidentally declare an Array when what I really want is an Object. I tend to forgot that associative Arrays in Javascript do not really exists, they just are Objects.